JP7379578B2 - Multilayer ceramic capacitor and method for manufacturing multilayer ceramic capacitor - Google Patents

Description

The present invention relates to a multilayer ceramic capacitor and a method for manufacturing the same.

In a multilayer ceramic capacitor, a technique for co-firing an external electrode and a multilayer body is known (see Patent Document 1). On the other hand, when the external electrode and the laminate are fired at the same time, the external electrode shrinks in volume at a lower temperature than the laminate during firing, which increases stress on the laminate and causes defects such as cracks. There was a problem.

Therefore, from the viewpoint of increasing the adhesive strength between the chip-like laminate and the Ni external electrode, Patent Document 2 discloses a laminate having an oxide layer of a (Ni, Mg) compound on the interface between the laminate and the Ni external electrode. Ceramic capacitors are listed. The oxidized layer is formed by adding Mg compound powder to dielectric ceramic powder and firing it in a predetermined oxygen partial pressure atmosphere.

Japanese Patent Application Publication No. 2005-44903 JP2009-172011A

However, in the multilayer ceramic capacitor described in Patent Document 2, there was a concern that if Mg added to the dielectric ceramic powder diffuses into the laminate during firing, it would lead to a decrease in electrical characteristics such as a decrease in capacity.

In view of the above circumstances, an object of the present invention is to provide a multilayer ceramic capacitor and a method for manufacturing the same that can obtain high reliability while maintaining electrical characteristics.

In order to achieve the above object, a multilayer ceramic capacitor according to one embodiment of the present invention includes a capacitance forming portion, a peripheral portion, an external electrode, and an oxide layer.
The capacitor forming section includes a plurality of ceramic layers formed of a dielectric material having a perovskite structure containing titanium and stacked in a uniaxial direction, and a plurality of internal electrodes arranged between the plurality of ceramic layers.
The peripheral portion includes a high magnesium region that covers the periphery of the capacitance forming portion and forms an outer surface, and a low magnesium region formed between the high magnesium region and the capacitance forming portion.
The external electrode is mainly made of nickel, is formed on the outer surface of the peripheral portion, and is connected to the plurality of internal electrodes.
The oxide layer includes nickel and magnesium and is formed between the high magnesium region and the external electrode.

With this configuration, the magnesium concentration is high near the outer surface of the peripheral portion, so that the magnesium diffused toward the external electrode side during firing reacts with nickel to form an oxide layer. Therefore, the ceramic body including the capacitance forming portion and the peripheral portion and the external electrode are bonded to each other via the oxide layer, and this bond is a bond between oxides. Therefore, a bond with higher affinity than that between a metal material and a ceramic material (oxide) is formed, and defects such as peeling and cracking at the bonding surface of the external electrode can be prevented.
Furthermore, the peripheral portion is configured such that the magnesium concentration is low near the capacitance forming portion. This can prevent magnesium, which may degrade the electrical characteristics of the capacitor forming portion, from diffusing into the capacitor forming portion. Therefore, it is possible to maintain high reliability in connection of external electrodes while maintaining electrical characteristics.

The low magnesium region may be formed with a thickness of 5 μm or more.
Thereby, diffusion of magnesium from the high-magnesium region to the capacitance forming portion can be more reliably prevented.

The magnesium concentration in the high magnesium region may be 0.6 mol% or more.
Thereby, a sufficiently thick oxide layer can be formed.

The magnesium concentration in the low magnesium region may be 0.3 mol% or less.
Thereby, deterioration of electrical characteristics due to magnesium in the capacitor forming portion can be more reliably prevented.

In a method for manufacturing a multilayer ceramic capacitor according to another embodiment of the present invention, an unfired ceramic body including a capacitance forming portion and a peripheral portion is manufactured. The capacitor forming section includes a plurality of ceramic layers formed of a dielectric material having a perovskite structure containing titanium and stacked in a uniaxial direction, and a plurality of internal electrodes arranged between the plurality of ceramic layers. The peripheral portion includes a high magnesium region that covers the periphery of the capacitance forming portion and forms an outer surface, and a low magnesium region formed between the high magnesium region and the capacitance forming portion.
An electrode material containing nickel as a main component is applied to the outer surface of the peripheral portion.
The ceramic body and the electrode material are co-fired.

As described above, according to the present invention, it is possible to provide a multilayer ceramic capacitor that maintains electrical characteristics and provides high reliability, and a method for manufacturing the same.

FIG. 1 is a perspective view of a multilayer ceramic capacitor according to a first embodiment of the present invention. 2 is a cross-sectional view of the multilayer ceramic capacitor taken along line AA' in FIG. 1. FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor taken along line BB' in FIG. 1. FIG. FIG. 2 is a schematic perspective view showing a mode in which external electrodes are removed from the multilayer ceramic capacitor. It is a flowchart which shows the manufacturing method of the said laminated ceramic capacitor. It is a perspective view showing the manufacturing process of the above-mentioned multilayer ceramic capacitor. It is a perspective view showing the manufacturing process of the above-mentioned multilayer ceramic capacitor. FIG. 3 is a cross-sectional view of a multilayer ceramic capacitor according to a second embodiment of the present invention. FIG. 2 is a schematic perspective view showing a mode in which external electrodes are removed from the multilayer ceramic capacitor. It is a flowchart which shows the manufacturing method of the said laminated ceramic capacitor. FIG. 3 is a plan view showing the manufacturing process of the multilayer ceramic capacitor. It is a perspective view showing the manufacturing process of the above-mentioned multilayer ceramic capacitor. It is a perspective view showing the manufacturing process of the above-mentioned multilayer ceramic capacitor. FIG. 7 is a cross-sectional view of a multilayer ceramic capacitor according to a modification of the second embodiment of the present invention. FIG. 2 is a schematic perspective view showing a mode in which external electrodes are removed from the multilayer ceramic capacitor. It is a perspective view showing the manufacturing process of the above-mentioned multilayer ceramic capacitor. It is a perspective view showing the manufacturing process of the above-mentioned multilayer ceramic capacitor. FIG. 3 is a perspective view of a multilayer ceramic capacitor according to a third embodiment of the present invention. 19 is a cross-sectional view of the multilayer ceramic capacitor taken along line CC' in FIG. 18. FIG. 19 is a cross-sectional view of the multilayer ceramic capacitor taken along line DD' in FIG. 18. FIG. FIG. 3 is a schematic exploded perspective view of a ceramic body of the multilayer ceramic capacitor. FIG. 2 is a schematic perspective view showing a mode in which external electrodes are removed from the multilayer ceramic capacitor. FIG. 7 is a cross-sectional view of a multilayer ceramic capacitor according to a modification of the third embodiment of the present invention. FIG. 2 is a schematic perspective view showing a mode in which external electrodes are removed from the multilayer ceramic capacitor.

Embodiments of the present invention will be described below with reference to the drawings.
In the drawings, mutually orthogonal X, Y, and Z axes are shown as appropriate. The X, Y, and Z axes are common to all figures.

<First embodiment>
[Basic configuration of multilayer ceramic capacitor 10]
1 to 3 are diagrams showing a multilayer ceramic capacitor 10 according to a first embodiment of the present invention. FIG. 1 is a perspective view of a multilayer ceramic capacitor 10. FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor 10 taken along line AA' in FIG. FIG. 3 is a cross-sectional view of the multilayer ceramic capacitor 10 taken along line BB' in FIG.

The multilayer ceramic capacitor 10 includes a ceramic body 11, a first external electrode 14, a second external electrode 15, and an oxide layer P1. The multilayer ceramic capacitor 10 has a configuration in which external electrodes 14 and 15 are formed on the surface of a ceramic body 11. Note that the configuration of the oxide layer P1 will be explained in "Detailed Configuration of Multilayer Ceramic Capacitor 10".

The outer surface of the ceramic body 11 typically has two end faces 11a and 11b facing the X-axis direction, two side faces 11c and 11d facing the Y-axis direction, and two main faces facing the Z-axis direction. It has surfaces 11e and 11f. External electrodes 14 and 15 are formed on the end surfaces 11a and 11b. The edges connecting the respective surfaces of the ceramic body 11 may be chamfered.
Note that the ceramic body 11 does not have to have a rectangular parallelepiped shape as shown in FIGS. 1 to 3. For example, each surface of the ceramic body 11 may be a curved surface, and the ceramic body 11 may have a rounded shape as a whole.

The ceramic body 11 includes a capacitor forming portion 16, end margin portions 17a and 17b, a cover portion 18, and a side margin portion 19.
The capacitor forming portion 16 includes a plurality of ceramic layers 20, a plurality of first internal electrodes 12, and a plurality of second internal electrodes 13, and has a structure in which these are stacked. The capacitor forming portion 16 has a function of storing electric charge in the multilayer ceramic capacitor 10.
The end margin parts 17a and 17b, the cover part 18, and the side margin part 19 constitute a peripheral part that covers the periphery of the capacitance forming part 16. More specifically, the end margin parts 17a and 17b cover the capacitance forming part 16 from the X-axis direction. The cover portion 18 covers the capacitance forming portion 16 from the Z-axis direction. The side margin portion 19 covers the capacitor forming portion 16 from the Y-axis direction.

The internal electrodes 12 and 13 are alternately arranged along the Z-axis direction between the plurality of ceramic layers 20 stacked in the Z-axis direction. The first internal electrode 12 is drawn out to the end surface 11a via the end margin portion 17a, and is spaced apart from the end surface 11b with the end margin portion 17b interposed therebetween. The second internal electrode 13 is drawn out to the end surface 11b via the end margin section 17b, and is spaced apart from the end surface 11a with the end margin section 17a in between.
The internal electrodes 12 and 13 are typically composed of nickel (Ni) as a main component, and function as internal electrodes of the multilayer ceramic capacitor 10. Note that the internal electrodes 12 and 13 may have at least one of copper (Cu), silver (Ag), and palladium (Pd) as a main component other than nickel.

The ceramic layer 20 is formed of a dielectric ceramic, specifically a perovskite-structured dielectric containing titanium. An example of a dielectric material having a perovskite structure containing titanium is a polycrystalline material of barium titanate (BaTiO ₃ )-based material. Thereby, the capacitance in the capacitor forming portion 16 can be increased. In addition, examples of the dielectric include strontium titanate (SrTiO ₃ ), calcium titanate (CaTiO ₃ ), calcium zirconate titanate (Ca(Zr,Ti)O ₃ ), and the like.

The cover portion 18 has a flat plate shape extending along the XY plane. The cover portion 18 is formed with main surfaces 11e and 11f as outer surfaces facing in the Z-axis direction. The side margin portion 19 has a flat plate shape extending along the XZ plane. Side margin portions 19 are formed with side surfaces 11c and 11d as outer surfaces facing in the Y-axis direction.

The cover part 18 and the side margin part 19 are formed of dielectric ceramics. The material forming the cover part 18 and the side margin part 19 may be any insulating ceramic, but internal stress in the ceramic body 11 is suppressed by using the same dielectric material as the ceramic layer 20.

The external electrodes 14 and 15 are mainly composed of nickel (Ni). The external electrodes 14 and 15 cover the end surfaces 11a and 11b of the ceramic body 11, respectively, and extend to four surfaces (side surfaces 11c and 11d and main surfaces 11e and 11f) connected to the end surfaces 11a and 11b. As a result, both of the external electrodes 14 and 15 have a U-shaped cross section parallel to the XZ plane and a cross section parallel to the XY plane. One or more plating films may be formed on the surfaces of the external electrodes 14 and 15 using the external electrodes 14 and 15 as a base film (not shown). This makes it easy to mount the multilayer ceramic capacitor 10.

With the above configuration, in the multilayer ceramic capacitor 10, when a voltage is applied between the first external electrode 14 and the second external electrode 15, a plurality of A voltage is applied to the ceramic layer 20. As a result, charges corresponding to the voltage between the first external electrode 14 and the second external electrode 15 are stored in the multilayer ceramic capacitor 10 .

Note that the basic configuration of the multilayer ceramic capacitor 10 according to this embodiment is not limited to the configurations shown in FIGS. 1 to 3, and can be modified as appropriate. For example, the number of internal electrodes 12 and 13 and the thickness of ceramic layer 20 can be determined as appropriate depending on the size and performance required of multilayer ceramic capacitor 10.

[Detailed configuration of multilayer ceramic capacitor 10]
The cover portion 18 includes a high magnesium region 181 formed on the main surfaces 11e and 11f, and a low magnesium region 182 formed adjacent to the high magnesium region 181 and the capacitance forming portion 16. That is, the cover part 18 has a two-layer structure with different magnesium concentrations, which is laminated on both sides in the Z-axis direction of a laminate including the capacitor forming part 16 and the side margin part 19.

High magnesium region 181 has a higher magnesium concentration than low magnesium region 182 and ceramic layer 20 . Magnesium contained in the high-magnesium region 181 is oxidized with nickel at the contact portions with the external electrodes 14 and 15 during sintering to form an oxide layer P1.
The magnesium concentration in the high magnesium region 181 is, for example, 0.6 mol % or more. By setting the magnesium concentration in this manner, it is possible to form the oxide layer P1 that can sufficiently increase the bonding strength with the external electrodes 14 and 15. The magnesium concentration may be 1.4 mol% or less. Thereby, the thickness of the oxide layer P1 can be controlled so that it does not reach the surfaces of the external electrodes 14 and 15.

The high magnesium region 181 is formed at a predetermined depth (thickness) from the main surfaces 11e and 11f. The depth can be set in consideration of the size of the multilayer ceramic capacitor 10, the bonding area with the external electrodes 14 and 15, etc., as long as it can appropriately ensure the thickness of the low magnesium region 182, which will be described later. The surface of the high magnesium region 181 extends downward in the Z-axis direction from the main surfaces 11e and 11f to part of the end surfaces 11a and 11b and the side surfaces 11c and 11d.

An oxide layer P1 is formed between the high magnesium region 181 and the external electrodes 14 and 15.
As described above, the external electrodes 14 and 15 are arranged on the end surfaces 11a and 11b of the capacitance forming portion 16 so as to be connected to the internal electrodes 12 and 13, and also on one of the main surfaces 11e and 11f and the side surfaces 11c and 11d. Extends to the end. Thereby, the external electrodes 14 and 15 are configured to partially cover the high magnesium region 181. The oxide layer P1 is formed in the region where the external electrodes 14 and 15 extend to the high magnesium region 181.

FIG. 4 is a schematic perspective view of the ceramic body 11 on which the oxide layer P1 is formed, showing a state in which the external electrodes 14 and 15 are removed from the multilayer ceramic capacitor 10. The broken lines in FIG. 4 indicate the range on the surface of the ceramic body 11 where the external electrodes 14 and 15 are formed. Further, in FIG. 4, illustration of the thickness of the oxide layer P1 is omitted.

The oxide layer P1 contains nickel and magnesium, and is typically composed of a ternary oxide containing nickel and magnesium. Since the external electrodes 14 and 15 are provided on the cover part 18 via the oxide layer P1, the oxide layer P1 and the cover part 18 made of oxide come into contact with each other. Thereby, the bonding strength between the external electrodes 14 and 15 and the cover portion 18 can be increased more than when the metal material and the dielectric ceramic, which is an oxide, are in direct contact with each other.

Further, the oxide layer P1 is formed to cover the boundaries between the main surfaces 11e and 11f, the end surfaces 11a and 11b, and the side surfaces 11c and 11d. More specifically, the oxide layer P1 extends over the entire length of the ceramic body 11 in the Y-axis direction near the boundaries between the main surfaces 11e and 11f and the end surfaces 11a and 11b, and at the boundaries between the main surfaces 11e and 11f and the side surfaces 11c and 11d. It is formed so as to straddle the boundary between the end faces 11a, 11b and the side faces 11c, 11d. With this configuration, the bonding strength of the external electrodes 14 and 15 can be increased at the boundary between the surfaces where peeling and cracking are particularly likely to occur, and the reliability of the multilayer ceramic capacitor 10 can be increased.

Low magnesium region 182 has a magnesium concentration lower than the magnesium concentration in high magnesium region 181. The magnesium concentration in the low magnesium region 182 is, for example, 0.3 mol % or less. Thereby, the low magnesium region 182 can be formed with substantially the same magnesium concentration as the ceramic layer 20 of the capacitor forming portion 16.

As shown in FIG. 3, the low magnesium region 182 is formed with a predetermined thickness D1 from the capacitor forming portion 16, for example, so that the thickness D1 is 5 μm or more. Note that when the thickness of the low magnesium region 182 is not constant, the thickness of the thinnest portion of the low magnesium region 182 is defined as the thickness D1.

Magnesium replaces titanium in the dielectric of the perovskite structure containing titanium during firing, and has the effect of lowering the dielectric constant ε of the dielectric. In the multilayer ceramic capacitor 10, by providing the low magnesium region 182 with a sufficient thickness, it is possible to prevent magnesium from diffusing from the high magnesium region 181 to the capacitance forming portion 16. This can prevent magnesium from acting on the dielectric and lowering the dielectric constant ε of the ceramic layer 20, and can prevent the capacitance of the multilayer ceramic capacitor 10 from lowering.

Furthermore, when magnesium diffuses to the internal electrodes, there is a possibility that nickel or the like, which is a material of the internal electrodes, reacts with magnesium, and oxides are formed at the ends of the internal electrodes 12 and 13. By providing the low magnesium region 182 to prevent magnesium from diffusing into the capacitor forming portion 16, oxidation of the internal electrodes can be prevented and a region capable of functioning as an electrode can be secured. Therefore, a decrease in the capacitance of the multilayer ceramic capacitor 10 can be further prevented.

[Method for manufacturing multilayer ceramic capacitor 10]
FIG. 5 is a flowchart showing a method for manufacturing the multilayer ceramic capacitor 10. 6 and 7 are diagrams showing the manufacturing process of the multilayer ceramic capacitor 10. A method for manufacturing the multilayer ceramic capacitor 10 will be described below along with FIG. 5 and with appropriate reference to FIGS. 6 and 7.

(Step S11: Preparation of unfired ceramic body 111)
In step S11, a first ceramic sheet 101 and a second ceramic sheet 102 for forming the capacitance forming part 16 and end margin parts 17a and 17b, and a third ceramic sheet 103 and a fourth ceramic sheet for forming the cover part 18 are formed. A sheet 104 is prepared. Then, as shown in FIG. 6, these ceramic sheets 101, 102, 103, and 104 are laminated to produce an unfired ceramic body 111.

The ceramic sheets 101, 102, 103, and 104 are configured as unfired dielectric green sheets whose main component is dielectric ceramic, which is a dielectric with a perovskite structure containing titanium. The ceramic sheets 101, 102, 103, and 104 are formed into a sheet shape using, for example, a roll coater or a doctor blade. The thickness of the ceramic sheets 101, 102, 103, 104 can be adjusted as appropriate.

As shown in FIG. 6, an unfired first internal electrode 112 corresponding to the first internal electrode 12 is formed on the first ceramic sheet 101, and an unfired first internal electrode 112 corresponding to the second internal electrode 13 is formed on the second ceramic sheet 102. A fired second internal electrode 113 is formed.

Internal electrodes 112, 113 can be formed by applying any conductive paste to ceramic sheets 101, 102. The method for applying the conductive paste can be arbitrarily selected from known techniques. For example, a screen printing method or a gravure printing method can be used to apply the conductive paste.

An unfired laminate 105 is produced by alternately stacking the ceramic sheets 101 and 102 in the Z-axis direction.
Note that the side margin portion 19 is formed by a laminated structure of regions of the ceramic sheets 101 and 102 outside the internal electrodes 112 and 113 in the Y-axis direction (unfired side margin portion 119 shown in FIG. 7).

On the other hand, no internal electrodes are formed on the ceramic sheets 103 and 104 corresponding to the cover part 18.
The ceramic sheets 103 and 104 have different magnesium concentrations. The magnesium concentration of the third ceramic sheet 103 is, for example, 0.3 mol % or less, and is equivalent to that of the ceramic sheets 101 and 102. A larger amount of magnesium (for example, 0.6 mol % or more) is added to the fourth ceramic sheet 104 than that of the third ceramic sheet 103. The third ceramic sheet 103 is used to form the low magnesium region 182 and the fourth ceramic sheet 104 is used to form the high magnesium region 181.

As shown in FIG. 6, the plurality of third ceramic sheets 103 are stacked on the upper and lower surfaces of the laminate 105 in the Z-axis direction. Furthermore, the plurality of fourth ceramic sheets 104 are stacked on the top and bottom surfaces of the stacked ceramic sheets 103 in the Z-axis direction. The laminated structure of the ceramic sheets 103 and 104 is configured as an unfired cover part 118 corresponding to the cover part 18. In the cover part 118, the laminated structure of the ceramic sheet 104 is configured as an unfired high magnesium region 118a, and the laminated structure of the ceramic sheet 103 is configured as an unfired low magnesium region 118b.

The unfired ceramic body 111 is integrated by pressing the ceramic sheets 101, 102, 103, and 104 together. For pressure bonding of the ceramic sheets 101, 102, 103, 104, it is preferable to use, for example, hydrostatic pressure, uniaxial pressure, or the like. Thereby, it is possible to increase the density of the ceramic body 111.

FIG. 7 is a perspective view of the unfired ceramic body 111 obtained in step S11. The unfired ceramic body 111 has a capacitance forming part (not shown) in which internal electrodes 112 and 113 are alternately stacked between ceramic layers 120, and the internal electrodes 112 and 113 are connected to each other through an end margin part 117. It is exposed on both end faces in the X-axis direction. The unfired ceramic body 111 has an unfired cover part 118 and an unfired side margin part 119 formed around the capacitance forming part, and is visible from both side surfaces in the Y-axis direction and both main surfaces in the Z-axis direction. Internal electrodes 112 and 113 are not exposed.

Although the unfired ceramic body 111 corresponding to one ceramic body 11 has been described above, in reality, a laminated sheet configured as a large sheet that is not separated into pieces is formed, and the ceramic body Each body 111 is separated into pieces.

(Step S12: Electrode material application)
In step S12, an electrode material is applied to the surface of the unfired ceramic body 111 obtained in step S11.

For example, an unfired electrode material is applied to both end faces of the unfired ceramic body 111. As the electrode material, for example, a conductive paste containing metal powder whose main component is nickel (Ni) is used. In addition to these, the electrode material may appropriately contain additives such as an organic binder.

A dip method is used as the coating method. Thereby, the electrode material can be applied so as to cover both end surfaces and reach the laminated portion of the fourth ceramic sheet 104 of the unfired cover portion 118. Alternatively, a screen printing method or a roll transfer method may be used.

(Step S13: Firing)
In step S13, the ceramic element 11 of the multilayer ceramic capacitor 10 shown in FIGS. 1 to 3 is manufactured by simultaneously sintering the unfired ceramic element 111 obtained in step S12 and the electrode material. That is, in step S13, the laminated body 105 of the ceramic sheets 101 and 102 becomes the capacitance forming part 16 and the side margin part 19, and the unfired cover part 118, which is the laminated structure of the ceramic sheets 103 and 104, becomes the cover part 18. .

In step S13, baking is performed under conditions such as predetermined temperature and time. The firing temperature can be, for example, about 1150 to 1400°C. Further, the firing can be performed under a predetermined oxygen partial pressure. The oxygen partial pressure can be, for example, 2.2*10 ^-4 Pa≦PO ₂ ≦6.2*10 ^-4 Pa at 1260°C. Note that, after performing the binder removal treatment, firing may be performed under the above oxygen partial pressure. Furthermore, after the firing, reoxidation treatment or the like may be performed.

In the firing process, a portion of the magnesium contained in the fourth ceramic sheet 104 (high magnesium region 118a) diffuses into the portion in contact with the electrode material. At this time, nickel forms an oxide while taking in magnesium and oxygen, so that an oxide layer P1 containing nickel and magnesium is formed at the portion where the fourth ceramic sheet 104 and the electrode material are in contact. As a result, the oxide layer P1 shown in FIGS. 1 to 4 is formed. On the other hand, since the third ceramic sheet 103 contains almost no magnesium, no oxide layer is formed at the portion where the third ceramic sheet 103 and the electrode material are in contact.

Since the fourth ceramic sheet 104 has a high magnesium concentration, nickel oxide can be stably formed by firing under a predetermined oxygen partial pressure. Furthermore, the dielectric ceramic after firing is an oxide. Therefore, due to the oxide layer P1, a part of the joint between the external electrodes 14 and 15 and the cover part 18 becomes a joint between oxides rather than a joint between a metal and an oxide. Therefore, the bonding strength between the external electrodes 14, 15 and the cover portion 18 can be increased, and peeling of the external electrodes 14, 15 and generation of cracks at the bonded portion can be prevented.

In addition, when firing the unfired electrode material and the unfired ceramic body 111 at the same time, due to the difference in sintering behavior between the electrode material and the dielectric ceramic, there is a large Stress occurs. That is, the electrode material starts sintering at a lower temperature (for example, several hundred degrees Celsius) than the ceramic body 111, and its volume begins to shrink. On the other hand, since dielectric ceramics are in an unsintered state at a temperature of several hundred degrees Celsius, volumetric shrinkage does not occur. As a result, stress is applied to the cover portion 18 made of dielectric ceramics and the ceramic layer 20 during firing, making it easy for the external electrodes 14 and 15 to peel off after firing and for cracks to occur at the joints with the ceramic body 11.

On the other hand, sintering of an oxide containing nickel and magnesium starts at a temperature similar to that of the electrode material, and almost no stress due to volumetric contraction occurs between the oxide and the electrode material. Therefore, the stress during firing can be alleviated, and peeling and cracking of the external electrodes 14 and 15 can be more effectively prevented.

Here, if all of the ceramic sheets 103 and 104 corresponding to the cover part 18 have a high magnesium concentration equivalent to that of the fourth ceramic sheet 104, there is a possibility that magnesium will diffuse toward the ceramic body 11 side during firing. . As mentioned above, magnesium also has the effect of lowering the dielectric constant ε of a dielectric having a perovskite structure containing titanium. Therefore, the diffusion of magnesium toward the ceramic body 11 side may reduce the capacitance of the capacitance forming portion 16.

Therefore, in this embodiment, the third ceramic sheet 103 with a low magnesium concentration is laminated on the unfired laminate 105 corresponding to the capacitance forming part 16. Thereby, a low magnesium region 182 is provided between the capacitance forming portion 16 and the high magnesium region 181, and diffusion of magnesium from the high magnesium region 181 toward the capacitance forming portion 16 can be prevented. Therefore, a decrease in the capacitance of the multilayer ceramic capacitor 10 can be prevented. In particular, by stacking the third ceramic sheets 103 so that the thickness D1 of the low magnesium region 182 after firing is 5 μm or more, a decrease in capacity can be more effectively prevented.

Note that one or more plated films may be formed by a plating process such as electrolytic plating using the fired external electrodes 14 and 15 as a base film. By adjusting the magnesium concentration of the fourth ceramic sheet 104, etc., it is possible to control the oxide layer P1 so that it does not reach the surfaces of the external electrodes 14 and 15, and a good plating film can be formed.

<Second embodiment>
In the first embodiment, the cover part 18 had a two-layer structure with different magnesium concentrations, but in addition to the cover part, the side margin part may also have a two-layer structure.
In addition, in the following description, the same code|symbol is attached|subjected about the structure similar to 1st Embodiment, and description is abbreviate|omitted.

[Configuration of multilayer ceramic capacitor 30]
8 and 9 are diagrams showing a multilayer ceramic capacitor 30 according to a second embodiment of the present invention. FIG. 8 is a cross-sectional view corresponding to FIG. 3 (the region where the first external electrode 14 is formed is cut along the YZ plane). FIG. 9 is a perspective view of the ceramic body 31, showing a state in which the external electrodes 14 and 15 are removed from the multilayer ceramic capacitor 30.
Note that the external appearance of the multilayer ceramic capacitor 30 and the configuration of a cross section taken along the Z-X plane at the center in the Y-axis direction of the multilayer ceramic capacitor 30 are similar to the structure of the multilayer ceramic capacitor 10 shown in FIGS. 1 and 2. Therefore, illustration is omitted.

The multilayer ceramic capacitor 30 includes a ceramic body 31, a first external electrode 14, a second external electrode 15, and an oxide layer P3.
The ceramic body 31 includes a capacitor forming portion 16, end margin portions 17a and 17b, a cover portion 38, and a side margin portion 39. The end margin parts 17a and 17b, the cover part 38, and the side margin part 39 constitute a peripheral part that covers the periphery of the capacitance forming part 16.

The cover portion 38 covers the capacitor forming portion 16 and the end margin portions 17a, 17b from both sides in the Z-axis direction. The cover portion 38 is formed with main surfaces 31e and 31f as outer surfaces facing in the Z-axis direction. In this embodiment, the cover portion 38 is formed so that its width in the Y-axis direction is approximately the same as that of the capacitance forming portion 16 . The side margin portion 39 covers the capacitor forming portion 16, the end margin portions 17a and 17b, and the cover portion 38 from both sides in the Y-axis direction. The side margin portion 39 has side surfaces 31c and 31d formed as outer surfaces facing in the Y-axis direction.

Similar to the cover part 18, the cover part 38 includes a first high-magnesium region 381 formed on the main surfaces 31e and 31f, and a first high-magnesium region 381 formed adjacent to the first high-magnesium region 381 and the capacitance forming part 16. 1 low magnesium region 382.

The first high magnesium region 381 has a higher magnesium concentration than the first low magnesium region 382, and has a concentration equivalent to, for example, the high magnesium region 181 of the first embodiment. The first low magnesium region 382 has a magnesium concentration lower than the first high magnesium region 381, for example, the same as that of the ceramic layer 20. The first low magnesium region 382 is preferably formed to have a thickness D21 in the Z-axis direction of 5 μm or more.

Similar to the cover portion 38, the side margin portion 39 includes a second high-magnesium region 391 formed on the side surfaces 31c and 31d, and a second high-magnesium region 391 formed adjacent to the second high-magnesium region 391 and the capacitance forming portion 16. 2 low magnesium region 392.

The second high magnesium region 391 has a higher magnesium concentration than the second low magnesium region 392, and has a concentration equivalent to, for example, the high magnesium region 181 of the first embodiment. The second high magnesium region 391 is formed at a predetermined depth (thickness) from the side surfaces 31c and 31d. The depth can be appropriately set depending on the size of the multilayer ceramic capacitor 30, the bonding area with the external electrodes 14 and 15, and the like.

The second low magnesium region 392 has a lower magnesium concentration than the second high magnesium region 391, and may have a concentration equivalent to that of the ceramic layer 20, for example. The second low magnesium region 392 is preferably formed to have a thickness D22 in the Y-axis direction of 5 μm or more.

The oxide layer P3 is formed between the first high magnesium region 381 of the cover part 18 and the external electrodes 14, 15, and between the second high magnesium region 391 of the side margin part 39 and the external electrodes 14, 15. Ru.
Like the oxide layer P1, the oxide layer P3 contains nickel and magnesium, and is typically composed of a ternary oxide containing nickel and magnesium.

The oxide layer P3 includes a first oxide region P31 formed corresponding to the first high magnesium region 381 and a second oxide region P32 formed corresponding to the second high magnesium region 391.
The first oxidized region P31 is formed at the boundary between the main surfaces 31e and 31f and the end surfaces 31a and 31b, and includes four portions facing each other in the Z-axis direction and the X-axis direction. The second oxidized region P32 is formed at the boundary between the side surfaces 31c and 31d and the end surfaces 31a and 31b, and extends over the entire length of the ceramic body 31 in the Z-axis direction at the periphery in contact with the end surfaces 31a and 31b of the side surfaces 31c and 31d, respectively. It is formed.
The second oxidized region P32 includes four portions facing each other in the Y-axis direction and the X-axis direction.

The oxide layer P3 of this embodiment covers the boundary between each surface of the ceramic body 31, making it possible to increase the bonding strength of the external electrodes 14 and 15 at the boundary where peeling and cracking are particularly likely to occur. can. In particular, since the oxide layer P3 is formed by the second oxidized region P32 at the periphery of the side surfaces 31c and 31d over the entire length of the ceramic body 31 in the Z-axis direction, a sufficient bonding area can be ensured. Therefore, the bonding strength between the external electrodes 14 and 15 can be further increased.

[Method for manufacturing multilayer ceramic capacitor 30]
FIG. 10 is a flowchart showing a method for manufacturing the multilayer ceramic capacitor 30. 11 to 13 are diagrams showing the manufacturing process of the multilayer ceramic capacitor 30.
The multilayer ceramic capacitor 30 is manufactured through steps S21, S12, and S13, which respectively correspond to steps S11 to S13 in the first embodiment, but the step S21 of manufacturing the unfired ceramic body 131 is the first step. This is different from step S11 of the first embodiment. Therefore, this step will be explained in detail.

(S21-1: Ceramic sheet preparation)
In step S21-1, first, a first ceramic sheet 301 and a second ceramic sheet 302 for forming the capacitance forming section 16 and end margin sections 17a and 17b, and a third ceramic sheet 303 and a second ceramic sheet for forming the cover section 38 are formed. A fourth ceramic sheet 304 is prepared. The ceramic sheets 301, 302, 303, and 304 are unfired dielectric green sheets whose main component is dielectric ceramic, which is a dielectric with a perovskite structure containing titanium. This is different from the first embodiment. Note that, like the ceramic sheets 103 and 104, the ceramic sheets 303 and 304 do not have internal electrodes formed thereon.

FIG. 11 is a plan view of the ceramic sheets 301 and 302. At this stage, the ceramic sheets 301 and 302 are configured as large sheets that are not separated into pieces. FIG. 11 shows cutting lines Lx and Ly when dividing each multilayer ceramic capacitor 10 into individual pieces. The cutting line Lx is parallel to the X-axis, and the cutting line Ly is parallel to the Y-axis.

As shown in FIG. 11, an unfired first internal electrode 312 corresponding to the first internal electrode 12 is formed on the first ceramic sheet 301, and an unfired first internal electrode 312 corresponding to the second internal electrode 13 is formed on the second ceramic sheet 302. A fired second internal electrode 313 is formed. These internal electrodes 312 and 313 are formed by a printing method or the like similarly to the internal electrodes 112 and 113.

The ceramic sheets 303 and 304 are large sheets corresponding to the ceramic sheets 103 and 104 of the first embodiment, respectively. The magnesium concentration of the third ceramic sheet 303 is, for example, 0.3 mol % or less, and is equivalent to that of the ceramic sheets 301 and 302. A larger amount of magnesium (for example, 0.6 mol % or more) is added to the fourth ceramic sheet 304 than that of the third ceramic sheet 303. The third ceramic sheet 303 is used to form the first low magnesium region 382 and the fourth ceramic sheet 304 is used to form the first high magnesium region 381.

(S21-2: Lamination)
In step S21-2, a laminated sheet 306 is produced by laminating ceramic sheets 301, 302, 303, and 304 as shown in FIG. The laminated sheet 306 is laminated in the same manner as the ceramic body 111 of the first embodiment. That is, the third ceramic sheet 303 is laminated on both sides of the stacked body 305 of ceramic sheets 301 and 302 in the Z-axis direction, and the fourth ceramic sheet 304 is laminated on both sides of the stacked third ceramic sheet 303 in the Z-axis direction. The laminated structure of the ceramic sheets 303 and 304 constitutes the unfired cover portion 138. The laminated structure of the third ceramic sheet 303 constitutes the first unfired low magnesium region 138b, and the laminated structure of the fourth ceramic sheet constitutes the first unfired high magnesium region 138a.
Ceramic sheets 301, 302, 303, and 304 are then pressure-bonded in the same manner as the ceramic body 111 of the first embodiment.

(S21-3: Cutting)
In step S21-3, the laminated sheet 306 is cut along the cutting lines Lx and Ly to produce an unfired laminated chip C (see FIG. 13). The laminated chip C corresponds to the capacitance forming portion 16, end margin portions 17a and 17b, and cover portion 38 after firing. For cutting the laminated sheet 306, for example, a push blade, a rotary blade, or the like can be used. In the laminated sheet 306, the ends of the internal electrodes are exposed on both side surfaces, which are cut surfaces.

(Step S21-4: Formation of side margin portion)
In step S21-4, unfired side margin portions 139 are provided on both sides in the Y-axis direction of the laminated chip C obtained in step S21-3, thereby producing an unfired ceramic body 131 shown in FIG. . The side margin portion 139 is formed from a ceramic material such as a ceramic sheet or ceramic slurry.

The side margin portion 139 can be formed, for example, by attaching a ceramic sheet to the side surface of the laminate. Further, the side margin portion 139 can also be formed by coating the side surface of the laminated chip C with a ceramic slurry, for example, by coating or dipping.

In this step, two ceramic materials with different magnesium concentrations are prepared as materials for the side margin portion 139. That is, a ceramic material with a high magnesium concentration (eg, 0.6 mol% or more) and a ceramic material with a low magnesium concentration (eg, 0.3 mol% or less) are prepared. First, a second low magnesium region 139b is provided on the side surface of the multilayer chip C using a ceramic material with a low magnesium concentration. Subsequently, a second high magnesium region 139a is provided on the second low magnesium region 139b using a ceramic material with a high magnesium concentration.

Through the above steps, the ceramic body 131 shown in FIG. 13 is manufactured.
Thereafter, as in the first embodiment, an electrode material is applied (step S12) and fired (step S13) to form an oxide layer P3, and the multilayer ceramic capacitor 30 is manufactured.
In this way, the multilayer ceramic capacitor 30 having a predetermined magnesium concentration distribution can be manufactured even by using the method of later attaching the unfired side margin portion 139 to the unfired ceramic body 131.

[Modified example]
FIG. 14 is a diagram showing a multilayer ceramic capacitor 40 according to a modification of the second embodiment of the present invention, and corresponds to FIGS. 3 and 8 (the region where the first external electrode 14 is formed is cut along the YZ plane Fig. 3 is a cross-sectional view of the
The multilayer ceramic capacitor 40 includes a ceramic body 41, a first external electrode 14, a second external electrode 15, and an oxide layer P4, and like the multilayer ceramic capacitor 30, a cover part 48 and a side margin part 49. Both have a two-layer structure with different magnesium concentrations. In this modification, the arrangement of the cover part 48, side margin part 49, and oxide layer P4 is different from the cover part 3, side margin part 49, and oxide layer P3 described above. Hereinafter, parts different from the second embodiment described above will be explained.

The side margin portions 49 cover the capacitor forming portion 16 from both sides in the Y-axis direction. The thickness of the side margin portion 49 in the Z-axis direction is the same as that of the capacitor forming portion 16 . The cover portion 48 covers the capacitor forming portion 16, the end margin portions 17a and 17b, and the side margin portion 49 from both sides in the Z-axis direction.

The cover part 48 has the same configuration as the cover part 18, and includes a first high magnesium region 481 formed on the main surfaces 41e and 41f, and a first high magnesium region 481 adjacent to the first high magnesium region 481 and the capacitance forming part 16. A first low magnesium region 482 is formed.

The side margin portion 49 also includes a second high magnesium region 491 formed on the side surfaces 41c and 41d, and a second low magnesium region 492 formed adjacent to the second high magnesium region 491 and the capacitance forming portion 16. has.

The second high magnesium region 491 of this modification is not continuous along the Z-axis direction but is divided. The second high-magnesium region 491 is formed on the same plane as the internal electrodes 12 and 13, faces each internal electrode at a distance in the Y-axis direction, and is configured in a band shape extending in the X-axis direction (see FIGS. 16 (see reference numeral M1). A second low magnesium region 492 having substantially the same thickness as the ceramic layer 20 is arranged between the second high magnesium regions 491 adjacent to each other in the Z-axis direction.

The second low magnesium region 492 includes a narrow layer sandwiched between the internal electrodes 12 and 13 and the second high magnesium region 491 along the Z-axis direction, and a wide layer that extends continuously from the ceramic layer 20 in the Y-axis direction. It is formed with a laminated structure of and. The width of the narrow layer along the Y-axis direction (thickness above the capacitor forming portion 16) is D22, which is the same as in the second embodiment.

As a result, an oxide layer P4 having a shape as shown in FIG. 15 is formed.
Specifically, the first oxidized region P41 of the oxide layer P4 has the same shape as the oxide layer P1 of the first embodiment, and the second oxidized region P42 of the oxide layer P4 has side surfaces 41c and 41d. It is formed at the boundary between the end surfaces 41a and 41b. That is, the oxide layer P4 of the multilayer ceramic capacitor 40 has a first oxidized region P41 having the same shape as the oxide layer P1 of the first embodiment, and further includes a second oxidized region P42. Therefore, the bonding strength with the external electrodes 14 and 15 can be further increased.

Although the second high-magnesium region 491 of the side margin portion 49 is divided in the Z-axis direction, the magnesium added to the second high-magnesium region 491 is diffused. Therefore, the second oxidized region P42 can be formed continuously in the Z-axis direction even within the formation range of the second high magnesium region 491.

Such a multilayer ceramic capacitor 40 is manufactured through the same steps S11 to S13 as the multilayer ceramic capacitor 10 of the first embodiment, but the side margin portion 49 is manufactured by changing the configuration of the ceramic sheet.

FIG. 16 is a diagram corresponding to FIG. 6 in step S11, and is an exploded perspective view of the process of laminating ceramic sheets 401, 402, 103, and 104 to produce an unfired ceramic body 141. Ceramic sheets 103 and 104 corresponding to the cover part 48 are laminated in the same manner as in the first embodiment, and constitute an unfired cover part 118. On the other hand, ceramic pastes having different magnesium concentrations are applied to the peripheries of the internal electrodes 112, 113 of the ceramic sheets 401, 402.

A low magnesium paste M2 is applied to positions adjacent to the internal electrodes 112 and 113 over the entire length of the ceramic sheets 401 and 402 in the X-axis direction. The magnesium concentration of the low magnesium paste M2 is equivalent to that of the ceramic material constituting the ceramic sheets 401 and 402 (for example, 0.3 mol % or less). On the outside of the low magnesium paste M2 in the Y-axis direction, a high-magnesium paste M1 with a high magnesium concentration (for example, 0.6 mol % or more) is applied over the entire length of the ceramic sheets 401 and 402 in the X-axis direction. A screen printing method or a gravure printing method can be used to apply these pastes M1 and M2. In addition, in FIG. 16, the low magnesium paste M2 is also applied to the end sides of the internal electrodes 112 and 113 in the X-axis direction (that is, the end margin parts 17a and 17b sides).

As described above, the unfired ceramic body 141 shown in FIG. 17 is produced, and then, as in the first embodiment, an electrode material is applied (step S12) and fired (step S13). In FIG. 17, regions with high magnesium concentration are shown as dots for explanation.
As a result, the second high-magnesium region 491 is formed by the high-magnesium paste M1. Further, a second low magnesium region 492 is formed by the region where the low magnesium paste M2 is applied and the end region of the unfired ceramic layer 120 on the outside in the Y-axis direction from the electrode formation region (capacitance formation portion 116). be done. Therefore, a multilayer ceramic capacitor 40 shown in FIG. 14 is manufactured.

<Third embodiment>
The present invention can also be applied to multi-terminal multilayer ceramic capacitors. As an example, a so-called three-terminal type multilayer ceramic capacitor 50 will be described.

18 to 20 are diagrams showing a multilayer ceramic capacitor 50 according to a third embodiment of the present invention. FIG. 18 is a perspective view of the multilayer ceramic capacitor 50. FIG. 19 is a cross-sectional view of the multilayer ceramic capacitor 50 taken along line CC' in FIG. FIG. 20 is a cross-sectional view of the multilayer ceramic capacitor 50 taken along line DD' in FIG. 18.
Hereinafter, the same components as those in the first and second embodiments described above will be denoted by the same reference numerals, and the description thereof will be omitted.

The multilayer ceramic capacitor 50 includes a ceramic body 51, a first external electrode 54, a second external electrode 55, a third external electrode 61, a fourth external electrode 62, and an oxide layer P5. The external electrodes 54 and 55 are also referred to as end surface external electrodes 54 and 55, and the external electrodes 61 and 62 are also referred to as side surface external electrodes 61 and 62.

The end surface external electrodes 54 and 55 are mainly made of nickel and are formed to cover the end surfaces 51a and 51b, similarly to the external electrodes 14 and 15 of the first embodiment. However, the end surface external electrodes 54 and 55 are both connected to a first internal electrode 52, which will be described later, and have the same polarity.

The side surface external electrodes 61 and 62 mainly contain nickel and are provided on the side surfaces 51c and 51d of the ceramic body 51, respectively. The side surface external electrodes 61 and 62 are each formed in a band shape extending in the Z-axis direction from one main surface 51e to the other main surface 51f. The side surface external electrodes 61 and 62 are both connected to a second internal electrode 53, which will be described later, and have the same polarity and different polarity from the end surface external electrodes 54 and 55.

The ceramic body 51 includes a capacitor forming portion 56 , a first end margin portion 57 , a cover portion 58 , and a second end margin portion 59 . The first end margin portion 57 , the cover portion 18 , and the second end margin portion 59 constitute a peripheral portion that covers the periphery of the capacitance forming portion 56 .

The capacitor forming portion 56 includes a plurality of ceramic layers 20, a plurality of first internal electrodes 52, and a plurality of second internal electrodes 53, and has a structure in which these are stacked. The capacitor forming portion 56 has a function of storing electric charge in the multilayer ceramic capacitor 50.

FIG. 21 is a schematic exploded perspective view of the ceramic body 51. Although the fired ceramic body 51 cannot actually be disassembled, FIG. 21 shows the ceramic body 51 disassembled for convenience of explanation.

The first internal electrode 52 is formed in a band shape extending over the entire length of the ceramic body 51 in the X-axis direction. The first internal electrode 52 is drawn out to the end surfaces 51a and 51b via the first end margin portion 57 and connected to the end surface external electrodes 54 and 55. The second internal electrode 53 is formed at the center in the XY plane. The second internal electrode 53 includes lead-out portions 53a and 53b extending to side surfaces 51c and 51d, respectively, via the second end margin portion 59, and is connected to the side surface external electrodes 61 and 62 by the lead-out portions 53a and 53b. Note that the width dimension in the Y-axis direction of the first internal electrode 52 and the width dimension in the Y-axis direction of the second internal electrode 53 excluding the lead-out portions 53a and 53b are formed to be substantially the same.

In the multilayer ceramic capacitor 50, when a voltage is applied between the end surface external electrodes 54, 55 and the side surface external electrodes 61, 62, the plurality of ceramic layers 20 between the first internal electrode 52 and the second internal electrode 53 Voltage is applied. Thereby, in the multilayer ceramic capacitor 50, electric charges are stored in accordance with the voltage between the end surface external electrodes 54, 55 and the side surface external electrodes 61, 62.

Similar to the cover part 18, the cover part 58 includes a high magnesium region 581 formed on the main surfaces 51e and 51f, and a low magnesium region 582 formed adjacent to the high magnesium region 581 and the capacitance forming part 56. , has.

The high magnesium region 581 has a magnesium concentration equivalent to, for example, the high magnesium region 181 of the first embodiment, and the low magnesium region 582 has a magnesium concentration lower than the high magnesium region 581, for example, equivalent to the ceramic layer 20. . The low magnesium region 582 is preferably formed to have a thickness of 5 μm or more in the Z-axis direction.

FIG. 22 is a perspective view of the ceramic body 51 on which the oxide layer P5 is formed, showing a state in which the external electrodes 54, 55, 61, and 62 are removed from the multilayer ceramic capacitor 50.
The oxide layer P5 is formed between the high magnesium region 581 of the cover portion 58 and the external electrodes 54, 55, 61, 62. Like the oxide layer P1, the oxide layer P5 contains nickel and magnesium, and is typically composed of a ternary oxide containing nickel and magnesium.

The oxide layer P5 is formed at the first oxide region P51 formed at the boundary between the end surfaces 51a, 51b, the side surfaces 51c, 51d, and the main surfaces 51e, 51f, and at the boundary between the side surfaces 51c, 51d and the main surfaces 51e, 51f. and a second oxidized region P52.

The first oxidized region P51 is configured similarly to the oxide layer P1 of the first embodiment. That is, the first oxidized region P51 includes four portions facing each other in the Z-axis direction and the X-axis direction, and is formed between the high magnesium region 581 and the end surface external electrodes 54 and 55. The first oxidized region P51 can increase the bonding strength of the external electrodes 14 and 15 at the boundary between the surfaces where peeling and cracking are particularly likely to occur.

The second oxidized region P52 is formed between the high magnesium region 581 and the side external electrodes 61 and 62, and includes four portions facing each other in the Z-axis direction and the Y-axis direction. The second oxidized region P52 is formed at the boundary between the side surfaces 51c and 51d and the main surfaces 51e and 51f at the center of the ceramic body 11 in the X-axis direction.

The second oxidized region P52 can also increase the bonding strength between the side surface external electrodes 61 and 62. That is, the side surface external electrodes 61 and 62 have a smaller contact surface with the ceramic body 51 than the external electrodes 14 and 15. Therefore, the side surface external electrodes 61 and 62 are likely to crack or peel off at the boundary between the side surfaces 51c and 51d and the main surfaces 51e and 51f. In this embodiment, by providing the second oxidized region P52, it is possible to increase the bonding strength of the side external electrodes 61 and 62, which are particularly susceptible to problems.

Note that the multilayer ceramic capacitor 50 is manufactured through the same steps S11 to S13 as the multilayer ceramic capacitor 10 of the first embodiment. However, the internal electrode patterns of the ceramic sheets 101 and 102 are changed to a shape corresponding to the internal electrodes 52 and 53 shown in FIG. 21.

[Modified example]
23 and 24 are diagrams showing a multilayer ceramic capacitor 70 according to a modification of the third embodiment of the present invention. FIG. 23 is a cross-sectional view taken along the YZ plane including the formation region of side external electrodes 61 and 62, similar to FIG. FIG. 24 is a perspective view of the ceramic body 71 on which the oxide layer P7 is formed, showing a state in which the external electrodes 54, 55, 61, and 62 are removed from the multilayer ceramic capacitor 70.
The multilayer ceramic capacitor 70 includes a ceramic body 71, a first external electrode 54, a second external electrode 55, a third external electrode 61, a fourth external electrode 62, and an oxide layer P7. In the multilayer ceramic capacitor 70, as will be described later, the second end margin portion 79 of the ceramic body 71 also has a two-layer structure with different magnesium concentrations, so the configuration of the oxide layer P7 is different from that of the above embodiment.

The ceramic body 71 includes a capacitor forming portion 56 , a first end margin portion 57 , a cover portion 58 , and a second end margin portion 79 . The first end margin portion 57, the cover portion 58, and the second end margin portion 79 constitute a peripheral portion in this modification.

The second end margin portion 79 includes a second high magnesium region 791 formed on the side surfaces 71c and 71d, and a second low magnesium region 792 formed adjacent to the second high magnesium region 791 and the capacitance forming portion 56. and has. Similar to the modification of the second embodiment, the second high magnesium region 791 is not continuous along the Z-axis direction but is divided. That is, the second high magnesium region 791 is formed on the same plane as the first internal electrodes 52, faces each first internal electrode 52 at a distance in the Y-axis direction, and is configured in a band shape extending in the X-axis direction. Ru. The second low magnesium region 792 includes a narrow layer sandwiched between the first internal electrode 52 and the second high magnesium region 791 along the Z-axis direction, and a wide layer that extends continuously from the ceramic layer 20 in the Y-axis direction. It is formed with a laminated structure of and.

As a result, an oxide layer P7 having a shape as shown in FIG. 24 and including a first oxidized region P71, a second oxidized region P72, and a third oxidized region P73 is formed.
Specifically, the first oxidized region P71 is formed at the boundary between the end surfaces 71a and 71b, the side surfaces 71c and 71d, and the main surfaces 71e and 71f, similar to the first oxidized region P51 of the third embodiment. The second oxidized region P72 is formed at the boundary between the side surfaces 71c and 71d and the main surfaces 71e and 71f, similar to the second oxidized region P52.

The third oxidized region P73 is formed between the second high magnesium region 791 of the second end margin section 79 and the external electrodes 61, 62, and is formed at the center of the side surfaces 71c, 71d. The third oxidized region P73 is formed to include a plurality of fragments divided in the Z-axis direction, and is arranged alternately in the Z-axis direction with the lead-out portions 53a and 53b of the second internal electrode 53 exposed from the side surfaces 71c and 71d. will be placed in Thereby, conduction between the second internal electrode 53 and the side external electrodes 61 and 62 can be ensured. As described above, methods for forming the discontinuous third oxidized region P73 include adjusting the magnesium concentration in the third oxidized region P73 and adjusting the depth from the side surfaces 71c and 71d of the third oxidized region P73. Examples include:

With this configuration, the third oxidized region P73 can be provided as the oxide layer P7 in addition to the second oxidized region P72, and the bonding reliability between the side external electrodes 61 and 62 can be further improved.
Note that the oxidized region may be formed not only in the second end margin section 79 but also in the first end margin section 57. Further, the oxidized region may be formed only in the first end margin portion 57. Furthermore, in the configurations of the first and second embodiments, an oxidized region may be formed in the end margin portion as in the third embodiment.

Although each embodiment of the present invention has been described above, the present invention is not limited only to the above-described embodiments, and it goes without saying that various changes can be made without departing from the gist of the present invention. For example, an embodiment of the present invention can be a combination of each embodiment.

For example, in each of the above embodiments, a configuration example in which the peripheral portion has two layers of different magnesium concentrations has been described, but the present invention is not limited to this. For example, the peripheral portion may have a region of three or more layers including at least a high magnesium region forming the outer surface and a low magnesium region adjacent to the capacitance forming portion. This also makes it possible to prevent magnesium from diffusing into the capacitance forming portion and suppress a decrease in capacitance.

Further, in the third embodiment, a so-called three-terminal type multilayer ceramic capacitor has been described, but a multi-terminal type multilayer ceramic capacitor having another configuration may be used.

Furthermore, in the multilayer ceramic capacitor, the capacitance forming section may be divided into a plurality of parts in the Z-axis direction. In this case, it is sufficient that the internal electrodes are arranged alternately along the Z-axis direction in each capacitance forming part, and the first internal electrode or the second internal electrode is arranged continuously in the part where the capacitance forming part is switched. Good too.

10... Multilayer ceramic capacitor 11, 31, 41, 51, 71... Ceramic element body 12, 13, 52, 53... Internal electrode 14, 15, 54, 55, 61, 62... External electrode 16, 56... Capacitance formation Parts 18, 38, 48, 58... Cover part 19, 39, 49... Side margin part 17a, 17b, 57, 79... End margin part P1, P3, P4, P5, P7... Oxidation material layer

Claims (6)

a capacitor forming section having a plurality of ceramic layers formed of a dielectric material having a perovskite structure containing titanium and stacked in a first axis direction; and a plurality of internal electrodes disposed between the plurality of ceramic layers;
The capacitance forming portion includes a high magnesium region located on the outside in a second axial direction perpendicular to the first axial direction, and a low magnesium region formed between the high magnesium region and the capacitance forming portion. first and second side margin parts that cover the capacitor forming part and the first and second side margin parts from the first axial direction; and first and second cover parts that cover the capacitor forming part and the first and second side margin parts from the first axial direction. a peripheral edge portion that covers the periphery of the capacitance forming portion;
first and second main surfaces configured by the first and second cover parts and facing in the first axial direction;
The high magnesium regions in the first and second side margins are configured by the first and second cover parts and the first and second side margin parts, respectively, and the high magnesium regions are arranged in the first axial direction and the second axial direction. first and second side surfaces formed entirely in a third axis direction perpendicular to the first axis and facing in the second axis direction;
The first and second cover parts and the first and second side margin parts are arranged around the plurality of internal electrodes that have been drawn out, and the high magnesium region in the first and second side margin parts is arranged in the first and second side margin parts. first and second end surfaces formed at the boundary between the first and second side surfaces and facing in the third axial direction;
a ceramic body having
an external electrode containing nickel as a main component, covering each of the first and second end faces and connected to the plurality of internal electrodes;
an oxide layer containing nickel and magnesium, formed between the high magnesium region and the external electrode on the first and second end surfaces, and spaced apart from the first and second main surfaces;
Equipped with
The high magnesium regions are alternately stacked with the low magnesium regions in the first axial direction on the first and second side surfaces and the first and second end surfaces.
Multilayer ceramic capacitor. The multilayer ceramic capacitor according to claim 1 ,
The high-magnesium region is arranged to face each of the plurality of internal electrodes in the second axis direction with the low-magnesium region in between. The multilayer ceramic capacitor according to claim 1 or 2 ,
The low magnesium region is formed with a thickness of 5 μm or more. The multilayer ceramic capacitor according to any one of claims 1 to 3 ,
The magnesium concentration in the high magnesium region is 0.6 mol% or more. The multilayer ceramic capacitor. The multilayer ceramic capacitor according to any one of claims 1 to 4 ,
The magnesium concentration in the low magnesium region is 0.3 mol% or less. The multilayer ceramic capacitor. a capacitor forming section having a plurality of ceramic layers formed of a dielectric material having a perovskite structure containing titanium and stacked in a first axis direction; and a plurality of internal electrodes disposed between the plurality of ceramic layers;
The capacitance forming portion includes a high magnesium region located on the outside in a second axial direction perpendicular to the first axial direction, and a low magnesium region formed between the high magnesium region and the capacitance forming portion. first and second side margin parts that cover the capacitor forming part and the first and second side margin parts from the first axial direction; and first and second cover parts that cover the capacitance forming part and the first and second side margin parts from the first axial direction. a peripheral edge portion that covers the periphery of the capacitance forming portion;
first and second main surfaces configured by the first and second cover parts and facing in the first axial direction;
The high-magnesium regions in the first and second side margins are configured by the first and second cover parts and the first and second side margin parts, respectively, and the high magnesium regions are arranged in the first axial direction and the second axial direction. first and second side surfaces formed entirely in a third axis direction perpendicular to the first axis and facing in the second axis direction;
The first and second cover parts and the first and second side margin parts are arranged around the plurality of drawn-out internal electrodes, and the high magnesium region in the first and second side margin parts is arranged around the plurality of internal electrodes. first and second end surfaces formed at the boundary between the first and second side surfaces and facing in the third axial direction;
An unfired ceramic body containing
Applying an electrode material containing nickel as a main component so as to cover each of the first and second end surfaces,
By co-firing the ceramic body and the electrode material, the ceramic body contains nickel and magnesium, is formed between the high magnesium region and the electrode material on the first and second end faces, and is formed between the high magnesium region and the electrode material on the first and second end faces. forming an oxide layer spaced apart from the second principal surface;
In the step of producing an unfired ceramic body, the high magnesium regions are alternately laminated with the low magnesium regions in the first axial direction on the first and second side surfaces and the first and second end surfaces.
Manufacturing method for multilayer ceramic capacitors.

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