Multilayer Ceramic Capacitors

Abstract

A multilayer ceramic capacitor that can achieve high reliability without impairing capacitance or sinterability is provided. [Solution] A multilayer ceramic capacitor includes a laminated portion, a side margin portion, and a joint portion. The laminated portion has a plurality of ceramic layers stacked in a first direction and a plurality of internal electrodes, primarily composed of nickel, disposed between the plurality of ceramic layers. The side margin portion covers the laminated portion from a second direction perpendicular to the first direction. The joint portion is disposed between the laminated portion and the side margin portion and has a higher magnesium concentration than the plurality of ceramic layers and the side margin portion.

Description

Technical Field

[0001] The present invention relates to a multilayer ceramic capacitor to which a side margin portion is attached later and a method for manufacturing the same.

Background Art

[0002] In a method for manufacturing a multilayer ceramic capacitor, a technique for attaching later a protection portion (side margin portion) for protecting the periphery of an internal electrode is known. For example, Patent Document 1 discloses a technique for producing a ceramic element in which an internal electrode is exposed on a side surface and providing a protection portion on the side surface of the ceramic element.

[0003] Further, Patent Document 2 discloses a technique for improving moisture resistance by generating an oxide compound in a region near the side surface of an internal electrode formed of Ni.

[0004] More specifically, in the technique described in Patent Document 2, ceramics having a high Mg content are used for the side gap portion before firing. Thereby, in the region near the side surface of the internal electrode, Ni generates an oxide compound together with Mg derived from the side gap portion, so that the boundary portion between the internal electrode and the side gap portion is filled and the moisture resistance is improved.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the protective part where the internal electrodes with a low firing temperature are not arranged, the sinterability tends to be low. In the protective part with insufficient sinterability, defects such as peeling are likely to occur. In order to ensure the sinterability in the protective part, it is effective to include a large amount of magnesium having an action of improving the sinterability in the protective part.

[0007] On the other hand, magnesium has an action of inhibiting grain growth during firing. For this reason, when a large amount of magnesium is contained in the ceramic layer arranged between the internal electrodes, the crystal grains in the ceramic layer become fine, and thus the capacitance tends to decrease. Therefore, in the ceramic layer, it is not preferable that the amount of magnesium is large.

[0008] In this regard, in the technique described in Patent Document 2, in order to ensure the sinterability of the side gap part while forming a sufficient oxidation compound, it is necessary to increase the amount of magnesium in the side gap part. However, when the amount of magnesium in the side gap part is large, the diffusion amount of magnesium into the ceramic layer during firing increases, and thus the capacitance tends to decrease.

[0009] In view of the above circumstances, an object of the present invention is to provide a multilayer ceramic capacitor capable of obtaining high reliability without impairing the capacitance and sinterability, and a method for manufacturing the same.

Means for Solving the Problems

[0010] In order to achieve the above object, a multilayer ceramic capacitor according to an aspect of the present invention includes a stacked portion, a side margin portion, and a joining portion. The stacked portion includes a plurality of ceramic layers stacked in a first direction, and a plurality of internal electrodes arranged between the plurality of ceramic layers and mainly composed of nickel. The side margin portion covers the stacked portion from a second direction orthogonal to the first direction. The joining portion is arranged between the stacked portion and the side margin portion, and has a higher magnesium concentration than the plurality of ceramic layers and the side margin portion. The plurality of internal electrodes may have an oxidized region adjacent to the joint portion and containing nickel and magnesium.

[0011] This configuration can be realized by making the magnesium concentration at the joint portion before firing higher than that of the plurality of ceramic layers and the side margin portion. In this multilayer ceramic capacitor, since magnesium diffuses from the joint portion to the stacked portion during firing, magnesium is accurately supplied to the region adjacent to the joint portion. For this reason, an oxidized region containing nickel and magnesium is efficiently formed in the plurality of internal electrodes. As a result, shorts between the plurality of internal electrodes are less likely to occur, and the reliability of the multilayer ceramic capacitor is improved. Further, in this multilayer ceramic capacitor, since magnesium also diffuses from the joint portion to the side margin portion during firing, the magnesium concentration in the side margin portion increases. Furthermore, since a joint portion having a higher magnesium concentration than the side margin portion is disposed between the side margin portion and the stacked portion, the movement of magnesium from the side margin portion to the stacked portion during firing is less likely to occur. Therefore, it is possible to achieve both a high magnesium concentration in the side margin portion and a low magnesium concentration in the stacked portion. Thus, in this multilayer ceramic capacitor, high reliability can be obtained without impairing the capacitance and sinterability.

[0012] In the central portion of the side margin portion in the second direction, the magnesium concentration may be higher than the central portion of the plurality of ceramic layers in the second direction. In this configuration, since the magnesium concentration in the side margin portion is high, good sinterability can be obtained in the side margin portion. Also, since the magnesium concentration of the plurality of ceramic layers is low, a large capacitance can be obtained.

[0013] In the plurality of ceramic layers and the side margin portion, the magnesium concentration may increase toward the joint portion.

[0014] In the method for manufacturing a multilayer ceramic capacitor according to one embodiment of the present invention, an unfired multilayer chip having a plurality of ceramic layers laminated in a first direction and a plurality of internal electrodes disposed between the plurality of ceramic layers is prepared. A ceramic body is produced by providing a side margin portion on a side surface of the multilayer chip facing a second direction orthogonal to the first direction through a joint portion having a higher magnesium concentration than the plurality of ceramic layers and the side margin portion. The ceramic body is fired.

Advantages of the Invention

[0015] It is possible to provide a multilayer ceramic capacitor and a method for manufacturing the same, which can obtain high reliability without impairing capacitance and sinterability.

Brief Description of the Drawings

[0016]

Figure 1

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Mode for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, an X-axis, a Y-axis, and a Z-axis that are orthogonal to each other are appropriately shown. The X-axis, Y-axis, and Z-axis are common throughout the figures.

[0018] [Overall Configuration of Multilayer Ceramic Capacitor 10] Figs. 1 to 3 are views showing a multilayer ceramic capacitor 10 according to an embodiment of the present invention. Fig. 1 is a perspective view of the multilayer ceramic capacitor 10. Fig. 2 is a cross-sectional view of the multilayer ceramic capacitor 10 taken along line A-A' of Fig. 1. Fig. 3 is a cross-sectional view of the multilayer ceramic capacitor 10 taken along line B-B' of Fig. 1.

[0019] The multilayer ceramic capacitor 10 includes a ceramic body 11, a first external electrode 14, and a second external electrode 15. The ceramic body 11 typically has two end faces facing in the X-axis direction, two side faces facing in the Y-axis direction, and two main faces facing in the Z-axis direction. The ridge portions connecting the respective faces of the ceramic body 11 are chamfered.

[0020] Note that the shape of the ceramic body 11 is not limited to the above. That is, the ceramic body 11 does not have to be in the shape of a rectangular parallelepiped as shown in Figs. 1 to 3. For example, each face of the ceramic body 11 may be a curved surface, and the ceramic body 11 may have a rounded shape as a whole.

[0021] The external electrodes 14 and 15 cover both end faces of the ceramic body 11 in the X-axis direction and extend to four surfaces (two main surfaces and two side surfaces) that are connected to both end faces in the X-axis direction. As a result, in either of the external electrodes 14 and 15, the cross-sectional shape parallel to the X-Z plane and the cross-sectional shape parallel to the X-Y plane are U-shaped.

[0022] The ceramic body 11 has a stacked portion 16, a side margin portion 17, and a joint portion 18. The side margin portion 17 covers the entire regions of both side surfaces of the stacked portion 16 facing the Y-axis direction. The joint portion 18 is disposed between the stacked portion 16 and the side margin portion 17 and joins the stacked portion 16 and the side margin portion 17.

[0023] The stacked portion 16 has a capacitance forming portion 19 and a cover portion 20. The cover portion 20 covers the upper and lower surfaces of the capacitance forming portion 19 in the Z-axis direction. The capacitance forming portion 19 has a plurality of ceramic layers 21, a plurality of first internal electrodes 12, and a plurality of second internal electrodes 13. The cover portion 20 is not provided with the internal electrodes 12 and 13.

[0024] The internal electrodes 12 and 13 are mainly composed of nickel (Ni) and are alternately arranged along the Z-axis direction between the plurality of ceramic layers 21. The first internal electrode 12 is connected to the first external electrode 14 and is spaced apart from the second external electrode 15. The second internal electrode 13 is connected to the second external electrode 15 and is spaced apart from the first external electrode 14.

[0025] Thus, in the ceramic body 11, the surfaces of the capacitance forming portion 19 other than both end faces in the X-axis direction where the external electrodes 14 and 15 are provided are covered by the side margin portion 17 and the cover portion 20. The side margin portion 17 and the cover portion 20 mainly have the function of protecting the periphery of the capacitance forming portion 19 and ensuring the insulation of the internal electrodes 12 and 13.

[0026] The ceramic layer 21 between the internal electrodes 12 and 13 in the capacitance forming section 19 is formed of a dielectric ceramic. In the multilayer ceramic capacitor 10, a dielectric ceramic with a high dielectric constant is used as the dielectric ceramic constituting the ceramic layer 21 in order to increase the capacitance in the capacitance forming section 19.

[0027] More specifically, in the multilayer ceramic capacitor 10, as the high-dielectric-constant dielectric ceramic constituting the ceramic layer 21, a polycrystal of a barium titanate (BaTiO 3 )-based material, that is, a polycrystal having a perovskite structure containing barium (Ba) and titanium (Ti) is used. Thereby, a large capacitance can be obtained in the multilayer ceramic capacitor 10.

[0028] Note that the ceramic layer 21 may be composed of a strontium titanate (SrTiO3)-based material, a calcium titanate (CaTiO 3 )-based material, a magnesium titanate (MgTiO 3 )-based material, a calcium zirconate (CaZrO 3 )-based material, a calcium zirconate titanate (Ca(Zr,Ti)O 3 )-based material, a barium zirconate (BaZrO 3 )-based material, a titanium oxide (TiO 2 )-based material, etc. It may be configured.

[0029] The side margin portion 17, the joining portion 18, and the cover portion 20 are also formed of a dielectric ceramic. The material for forming the side margin portion 17, the joining portion 18, and the cover portion 20 may be an insulating ceramic, but using the same dielectric ceramic as the ceramic layer 21 suppresses the internal stress in the ceramic element 11.

[0030] 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 voltage is applied to the plurality of ceramic layers 21 between the first internal electrode 12 and the second internal electrode 13. As a result, in the multilayer ceramic capacitor 10, charges corresponding to the voltage between the first external electrode 14 and the second external electrode 15 are stored.

[0031] Note that the configuration of the multilayer ceramic capacitor 10 according to the present embodiment is not limited to the configurations shown in FIGS. 1 to 3 and can be changed as appropriate. For example, the number of internal electrodes 12 and 13 and the thickness of the ceramic layer 21 can be appropriately determined according to the size and performance required for the multilayer ceramic capacitor 10.

[0032] [Details of the ceramic body 11] FIG. 4 is a graph showing the distribution of magnesium (Mg) concentration along the Y-axis direction in a cross section parallel to the Y-Z plane of the ceramic body 11. In FIG. 4, the magnesium concentration in the laminated portion 16 is shown as the magnesium concentration at the central portion in the Z-axis direction of the ceramic layer 21.

[0033] As shown in FIG. 4, the distribution of magnesium concentration along the Y-axis direction in the ceramic body 11 has a peak at the joint portion 18. That is, in the ceramic body 11, the magnesium concentration is higher at the joint portion 18 than in the ceramic layer 21 and the side margin portion 17.

[0034] More specifically, the ceramic layer 21 has a concave distribution of magnesium concentration. That is, the magnesium concentration of the ceramic layer 21 increases from the central portion in the Y-axis direction toward the joint portion 18. Therefore, in the ceramic layer 21, the magnesium concentration is low at the central portion in the Y-axis direction and high in the region adjacent to the joint portion 18.

[0035] Magnesium has the effect of suppressing the grain growth of the ceramic layer 21 during firing. Therefore, in the ceramic layer 21, large crystal grains are likely to be obtained at the central portion in the Y-axis direction where the magnesium concentration is low. As a result, the relative dielectric constant ε in each ceramic layer 21 increases, so that the capacitance is easily ensured in the multilayer ceramic capacitor 10.

[0036] Also, in the laminated portion 16, in the region adjacent to the joint portion 18 where a short circuit is likely to occur between the internal electrodes 12 and 13, the magnesium concentration of the ceramic layer 21 is high, and the crystal grains of the ceramic layer 21 are kept small. As a result, high insulation between the internal electrodes 12 and 13 is obtained, so that the reliability of the multilayer ceramic capacitor 10 is improved.

[0037] FIG. 5 is a partial cross-sectional view showing an enlarged view of the region P surrounded by the one-dot chain line in FIG. 3 of the ceramic body 11. In the region adjacent to the joint portion 18 of the internal electrodes 12 and 13, conductive oxide regions 12a and 13a are formed. The oxide regions 12a and 13a contain nickel and magnesium, and are typically composed of a ternary oxide containing nickel and magnesium.

[0038] With this configuration, even when a conductive foreign substance adheres to the side surface of the laminated portion 16 facing the Y-axis direction during the manufacturing process of the multilayer ceramic capacitor 10, or when the oxide regions 12a and 13a come close to or contact each other due to deformation of the laminated portion 16, a short circuit between the internal electrodes 12 and 13 is less likely to occur. As a result, the reliability of the multilayer ceramic capacitor 10 is further improved.

[0039] Also, magnesium has the effect of improving the sinterability of the dielectric ceramics. Therefore, in the side margin portion 17 where it is difficult to ensure sinterability compared to the ceramic layer 21, it is preferable to increase the magnesium concentration higher than that of the ceramic layer 21. Thereby, defects such as peeling of the side margin portion 17 from the laminated portion 16 can be prevented.

[0040] The magnesium concentrations of the ceramic layer 21 and the side margin portion 17 can be compared, for example, at the central portion in the Y-axis direction. That is, the magnesium concentration at the central portion in the Y-axis direction of the side margin portion 17 can be made higher than the magnesium concentration at the central portion in the Y-axis direction of the ceramic layer 21.

[0041] Further, in the side margin portion 17, since heat is more likely to be applied during firing toward the outer side in the Y-axis direction, sinterability is easily ensured. For this reason, as shown in FIG. 4, in the side margin portion 17, it is preferable that the magnesium concentration decreases from the joint portion 18 toward the outer side in the Y-axis direction. Thereby, the amount of magnesium used can be suppressed.

[0042] [Manufacturing Method of Multilayer Ceramic Capacitor 10] FIG. 6 is a flowchart showing the manufacturing method of the multilayer ceramic capacitor 10. FIGS. 7 to 12 are diagrams showing the manufacturing process of the multilayer ceramic capacitor 10. Hereinafter, the manufacturing method of the multilayer ceramic capacitor 10 will be described with reference to FIGS. 7 to 12 as appropriate along FIG. 6.

[0043] (Step S01: Preparation of Ceramic Sheets) In step S01, a first ceramic sheet 101 and a second ceramic sheet 102 for forming the capacitance forming portion 19, and a third ceramic sheet 103 for forming the cover portion 20 are prepared. The ceramic sheets 101, 102, 103 are configured as unfired dielectric green sheets mainly composed of dielectric ceramics.

[0044] The ceramic sheets 101, 102, 103 are formed into a sheet shape using, for example, a roll coater or a doctor blade. It is not essential for the ceramic sheets 101, 102 to contain magnesium, but a small amount of magnesium may be contained as necessary.

[0045] FIG. 7 is a plan view of the ceramic sheets 101, 102, and 103. At this stage, the ceramic sheets 101, 102, and 103 are configured as large-sized sheets that have not been singulated. In FIG. 7, cutting lines Lx and Ly for singulating each multilayer ceramic capacitor 10 are shown. The cutting line Lx is parallel to the X-axis, and the cutting line Ly is parallel to the Y-axis.

[0046] As shown in FIG. 7, an unfired first internal electrode 112 corresponding to the first internal electrode 12 is formed on the first ceramic sheet 101, and an unfired second internal electrode 113 corresponding to the second internal electrode 13 is formed on the second ceramic sheet 102. Note that no internal electrode is formed on the third ceramic sheet 103 corresponding to the cover portion 20.

[0047] The internal electrodes 112 and 113 can be formed by applying an arbitrary conductive paste to the ceramic sheets 101 and 102. The method of 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 for applying the conductive paste.

[0048] In the internal electrodes 112 and 113, gaps in the X-axis direction along the cutting line Ly are formed every other cutting line Ly. The gaps of the first internal electrode 112 and the gaps of the second internal electrode 113 are arranged alternately in the X-axis direction. That is, the cutting lines Ly passing through the gaps of the first internal electrode 112 and the cutting lines Ly passing through the gaps of the second internal electrode 113 are arranged alternately.

[0049] (Step S02: Lamination) In step S02, a laminated sheet 104 is produced by laminating the ceramic sheets 101, 102, and 103 prepared in step S01 as shown in FIG. 8. In the laminated sheet 104, the first ceramic sheet 101 and the second ceramic sheet 102 corresponding to the capacitance forming portion 19 are laminated alternately in the Z-axis direction.

[0050] In the laminated sheet 104, third ceramic sheets 103 corresponding to the cover portions 20 are laminated on the upper and lower surfaces in the Z-axis direction of the alternately laminated ceramic sheets 101 and 102. In the example shown in FIG. 8, three third ceramic sheets 103 are laminated respectively, but the number of the third ceramic sheets 103 can be changed as appropriate.

[0051] The laminated sheet 104 is integrated by crimping the ceramic sheets 101, 102, and 103. For the crimping of the ceramic sheets 101, 102, and 103, it is preferable to use, for example, hydrostatic pressure pressing or uniaxial pressing. Thereby, it is possible to increase the density of the laminated sheet 104.

[0052] (Step S03: Cutting) In step S03, the laminated sheet 104 obtained in step S02 is cut along the cutting lines Lx and Ly as shown in FIG. 9 to produce an unfired laminated chip 116. The laminated chip 116 corresponds to the laminated portion 16 after firing. For cutting the laminated sheet 104, for example, a rotary blade or a push-cutting blade can be used.

[0053] More specifically, the laminated sheet 104 is cut along the cutting lines Lx and Ly while being held by the holding member C. Thereby, the laminated sheet 104 is separated into individual pieces, and the laminated chip 116 is obtained. At this time, the holding member C is not cut, and each laminated chip 116 is connected by the holding member C.

[0054] FIG. 10 is a perspective view of the laminated chip 116 obtained in step S03. A capacitance forming portion 119 and a cover portion 120 are formed in the laminated chip 116. In the laminated chip 116, the internal electrodes 112 and 113 are exposed on both side surfaces facing the Y-axis direction which is the cutting surface. A ceramic layer 121 is formed between the internal electrodes 112 and 113.

[0055] (Step S04: Side margin portion formation) In step S04, an unfired ceramic body 111 is produced by providing an unfired side margin portion 117 via an unfired joint portion 118 on the side surfaces of the laminated chip 116 obtained in step S03 where the internal electrodes 112 and 113 are exposed. The side margin portion 117 is formed from a ceramic sheet.

[0056] In step S04, side margin portions 117 are provided on both side surfaces facing the Y-axis direction which is the cut surface of the laminated chip 116 in step S03. For this reason, in step S04, it is preferable to previously peel the laminated chip 116 from the holding member C and rotate the orientation of the laminated chip 116 by 90 degrees.

[0057] In the joint portion 118, the magnesium concentration is higher than that of the ceramic sheets 101 and 102 constituting the ceramic layer 121 and the ceramic sheet constituting the side margin portion 117. Thereby, the joint portion 118 functions as a supply source of magnesium for the laminated chip 116 and the side margin portion 117 during firing.

[0058] If sufficient sinterability cannot be obtained only with the magnesium supplied from the joint portion 118 during firing, the ceramic sheet forming the side margin portion 117 may contain a predetermined amount of magnesium in advance. The magnesium concentration of the side margin portion 117 can be appropriately determined within a range lower than that of the joint portion 118.

[0059] Further, the joint portion 118 has a function of favorably bonding the laminated chip 116 and the side margin portion 117 and preventing the occurrence of cracks, peeling, etc. in the laminated chip 116 and the side margin portion 117 during firing. A specific example of the configuration of the joint portion 118 for realizing this function will be described in the next section (step S05).

[0060] (Step S05: Firing) In step S05, the unfired ceramic body 111 obtained in step S04 is sintered to produce the ceramic body 11 of the multilayer ceramic capacitor 10 shown in FIGS. 1 to 3. That is, by step S05, the laminated chip 116 becomes the laminated portion 16, the side margin portion 117 becomes the side margin portion 17, and the joint portion 118 becomes the joint portion 18.

[0061] The firing temperature in step S05 can be determined based on the sintering temperature of the ceramic body 111. For example, when a barium titanate-based material is used as the dielectric ceramics, the firing temperature can be set to about 1000 to 1300°C. Further, the firing can be performed, for example, in a reducing atmosphere or in an atmosphere with a low oxygen partial pressure.

[0062] FIG. 12 is a partial cross-sectional view showing the diffusion behavior of magnesium during firing. As shown in FIG. 12, magnesium contained in the joint portion 118 diffuses into both the laminated chip 116 and the side margin portion 117. Thereby, in the ceramic body 11 after firing, a characteristic magnesium concentration distribution as shown in FIG. 4 is obtained.

[0063] Also, as shown in FIG. 12, during firing, magnesium contained in the joint portion 118 is supplied to the Y-axis direction ends of the internal electrodes 112, 113, and nickel constituting the internal electrodes 112, 113 takes in magnesium and oxygen, and oxidation regions 12a, 13a are formed. The oxidation regions 12a, 13a grow toward the central portion in the Y-axis direction during firing.

[0064] In this way, by increasing the magnesium concentration in the joint portion 118, magnesium can be accurately supplied to the regions where the oxidation regions 12a, 13a are formed in the internal electrodes 112, 113. Thereby, the oxidation regions 12a, 13a can be efficiently and surely formed in the internal electrodes 112, 113.

[0065] Further, since the magnesium concentration at the joint portion 118 is higher than that of the side margin portion 117 and the ceramic layer 121, the movement of magnesium from the side margin portion 117 to the ceramic layer 121 is less likely to occur. That is, the joint portion 118 functions as a barrier layer that prevents the movement of magnesium from the side margin portion 117 to the ceramic layer 121.

[0066] As a result, even when the side margin portion 117 contains more magnesium than the ceramic layer 121, it is possible to prevent the magnesium contained in the side margin portion 117 from diffusing into the ceramic layer 121. Thereby, in the side margin portion 117, since the magnesium concentration is maintained, sinterability can be ensured.

[0067] Also, since it is possible to prevent a large amount of magnesium from diffusing from the side margin portion 117 to the ceramic layer 121, it is possible to suppress a decrease in the relative dielectric constant ε in the ceramic layer 21. Therefore, in the multilayer ceramic capacitor 10 obtained by this manufacturing method, capacitance can be ensured.

[0068] As described above, the joint portion 118 has a function of favorably bonding the stacked chip 116 and the side margin portion 117 and preventing the side margin portion 117 from peeling off from the stacked chip 116 during firing. The configuration of the joint portion 118 for realizing this function is not limited to a specific one. Hereinafter, specific examples of the configuration of the joint portion 118 will be described.

[0069] The joint portion 118 can be configured to use dielectric ceramics having an average particle size smaller than that of the stacked chip 116 and the side margin portion 117. Thereby, the joint portion 118 bites into the fine uneven shapes of the stacked chip 116 and the side margin portion 117, and the adhesion of the joint portion 118 to the stacked chip 116 and the side margin portion 117 is improved.

[0070] In addition, in the joint portion 118 composed of dielectric ceramics with a small average particle size, since it can be deformed flexibly during firing, the difference in shrinkage behavior between the laminated chip 116 and the side margin portion 117 can be alleviated. As a result, the occurrence of cracks, peeling, etc. in the laminated chip 116 and the side margin portion 117 can be prevented.

[0071] The average particle size of the dielectric ceramics constituting the laminated chip 116, the side margin portion 117, and the joint portion 118 can be appropriately determined. As an example, the average particle size of the dielectric ceramics constituting the laminated chip 116 and the side margin portion 117 can be several hundred nm, and the average particle size of the dielectric ceramics constituting the joint portion 118 can be several tens of nm.

[0072] Also, by containing silicon in the joint portion 118, the difference in shrinkage behavior between the laminated chip 116 and the side margin portion 117 during firing can be alleviated. That is, in the joint portion 118 having this configuration, since silicon generates a molten phase while incorporating surrounding components during firing, it can be deformed flexibly.

[0073] (Step S06: External electrode formation) In step S06, the laminated ceramic capacitor 10 shown in FIGS. 1 to 3 is manufactured by forming external electrodes 14 and 15 on the ceramic green body 11 obtained in step S05. In step S06, for example, a base film, an intermediate film, and a surface film constituting the external electrodes 14 and 15 are formed on the end faces in the X-axis direction of the ceramic green body 11.

[0074] More specifically, in step S06, first, an unfired electrode material is applied so as to cover both end faces in the X-axis direction of the ceramic green body 11. The applied unfired electrode material is baked, for example, in a reducing atmosphere or an atmosphere with a low oxygen partial pressure, whereby a base film of the external electrodes 14 and 15 is formed on the ceramic green body 11.

[0075] Then, an intermediate film of the external electrodes 14 and 15 is formed on the base films of the external electrodes 14 and 15 baked on the ceramic body 11, and further, a surface film of the external electrodes 14 and 15 is formed. For the formation of the intermediate film and the base film of the external electrodes 14 and 15, for example, plating treatment such as electrolytic plating can be used.

[0076] Note that a part of the process in step S06 may be performed before step S05. For example, an unfired electrode material may be applied to both end faces in the X-axis direction of the unfired ceramic body 111 before step S05. Thereby, in step S05, firing of the unfired ceramic body 111 and baking of the electrode material can be performed simultaneously.

[0077] [Embodiment] (Production of Sample) As an example of this embodiment, a sample of the multilayer ceramic capacitor 10 was produced using the above manufacturing method. In this sample, the dimension in the X-axis direction was 1 mm, and the dimensions in the Y-axis direction and the Z-axis direction were 0.5 mm. Also, in this sample, a barium titanate-based material was used as the dielectric ceramics.

[0078] Analysis of the magnesium concentration was performed on a cross-section parallel to the Y-Z plane in the ceramic body 11 of the sample according to this example. For the analysis of the magnesium concentration, laser ablation ICP mass spectrometry (LA-ICP-MS: Laser Ablation Inductively Coupled Plasma Mass Spectrometry) was used.

[0079] In laser ablation ICP mass spectrometry, dielectric ceramics in a minute region of the cross-section of the ceramic body 11 are evaporated and atomized, and further, ions generated by ionization are measured with a mass spectrometer. Thereby, the composition of the minute region in the cross-section of the ceramic body 11 can be analyzed.

[0080] In this example, 24Mg, which accounts for 78.70% in the natural isotope ratio, was used for the analysis of the magnesium concentration. Also, as a reference for the magnesium concentration, 47Ti, which is an isotope of titanium contained in a large amount in the dielectric ceramics, was used.

[0081] In this example, the magnesium concentration was analyzed at 15-μm intervals in the Y-axis direction for the side margin portion 17, the joint portion 18, and the stacked portion 16. The analysis of the magnesium concentration in the stacked portion 16 was performed in a minute region centered on the central portion in the Z-axis direction of the ceramic layer 21.

[0082] FIG. 13 is a graph showing the distribution of the magnesium concentration along the Y-axis direction in a cross section parallel to the Y-Z plane of the ceramic body 11 of the sample according to this example. The horizontal axis in FIG. 13 indicates the position in the Y-axis direction in the ceramic body 11.

[0083] More specifically, on the horizontal axis in FIG. 13, the central portion in the Y-axis direction of the joint portion 18 is set as "0", the position of the side margin portion 17 is shown in the minus region, and the position of the stacked portion 16 is shown in the plus region. That is, the horizontal axis in FIG. 13 indicates the distance from the central portion in the Y-axis direction of the joint portion 18.

[0084] The vertical axis in FIG. 13 indicates the magnesium concentration at each position of the side margin portion 17, the joint portion 18, and the stacked portion 16. In FIG. 13, the magnesium concentration at the position 105 μm in the Y-axis direction in the stacked portion 16 is set as 1, and the magnesium concentration at each position is shown in a normalized manner. Therefore, the vertical axis in FIG. 13 is in arbitrary units.

[0085] As shown in FIG. 13, in the stacked portion 16 and the side margin portion 17 of the sample according to this example, the magnesium concentration increases toward the joint portion 18. Therefore, in this example, it was confirmed that by using the above manufacturing method, the distribution of the magnesium concentration as shown in FIG. 4 in the ceramic body 11 of the multilayer ceramic capacitor 10 can be realized.

[0086] (Evaluation of Sample) Samples 1 to 4 prepared under conditions where the magnesium concentration in the joint 118 before firing was different were evaluated for the short circuit rate.

[0087] The magnesium concentration in the joint 118 was set to 0 atm% for Sample 1, 0.95 atm% for Sample 2, 4.75 atm% for Sample 3, and 9.5 atm% for Sample 4. That is, Sample 1 in which the joint 118 does not contain magnesium is a comparative example of the present embodiment, and Samples 2 to 4 are examples of the present embodiment. The concentration (atm%) is the concentration when the B site of the main component ceramics having a perovskite structure represented by the general formula ABO3 is 100 atm% in the dielectric ceramics used for the joint 118.

[0088] The evaluation of the short circuit rate was performed using an LCR meter under the condition of applying a voltage with Osc (Oscillation level) of 0.5 V and a frequency of 1 kHz. Each of the 200 samples 1 to 4 was evaluated, and the ratio of the number of samples in which a short circuit occurred among the 200 samples 1 to 4 was defined as the short circuit rate.

[0089] As a result, the short circuit rate of Sample 1 according to the comparative example was 50%. In Sample 1, since the joint 18 does not contain magnesium, sufficient oxidation regions 12a and 13a are not formed in the internal electrodes 12 and 13, and it is considered that a short circuit between the internal electrodes 12 and 13 is likely to occur.

[0090] On the other hand, the short circuit rate of Sample 2 was 10%, the short circuit rate of Sample 3 was 7%, and the short circuit rate of Sample 4 was 3%. That is, it was confirmed that in Samples 2 to 4 according to the examples, the short circuit rate was within 10%, and high reliability was obtained.

[0091] In addition, when the capacitances of Samples 2 to 4 were evaluated, sufficient capacitances were obtained for all of Samples 2 to 4. However, in order to obtain a large capacitance in the multilayer ceramic capacitor 10, it was confirmed that it is preferable to keep the magnesium concentration at the joint 118 at 9.5 atm% or less.

[0092] [Other Embodiments] As described above, the embodiments of the present invention have been described. However, the present invention is not limited only to the above-described embodiments, and it goes without saying that various modifications can be made.

[0093] For example, in the multilayer ceramic capacitor 10, the capacitance forming portion 19 may be provided by being divided into a plurality in the Z-axis direction. In this case, it is sufficient that the internal electrodes 12 and 13 are alternately arranged along the Z-axis direction in each capacitance forming portion 19, and the first internal electrode 12 or the second internal electrode 13 may be continuously arranged at the portion where the capacitance forming portion 19 switches.

Description of Reference Numerals

[0094] 10... Multilayer ceramic capacitor 11... Ceramic body 12, 13... Internal electrodes 14, 15... External electrodes 16... Laminated portion 17... Side margin portion 19... Capacitance forming portion 20... Cover portion 21... Ceramic layer

Claims

1. a laminated section including a plurality of ceramic layers laminated in a first direction and a plurality of internal electrodes, the internal electrodes being disposed between the plurality of ceramic layers and containing nickel as a main component; a side margin portion covering the laminated portion from a second direction perpendicular to the first direction; a high concentration layer disposed between the laminated portion and the side margin portion, the high concentration layer having a magnesium concentration higher than the plurality of ceramic layers and the side margin portion; Equipped with the high concentration layer is denser than the side margin portion, The average grain size of the dielectric ceramics contained in the high concentration layer is smaller than the average grain size of the dielectric ceramics contained in the ceramic layers in the laminated portion and smaller than the average grain size of the dielectric ceramics contained in the side margin portion. Multilayer ceramic capacitor.

2. 2. The multilayer ceramic capacitor according to claim 1, A region of the plurality of ceramic layers adjacent to the high concentration layer has a higher magnesium concentration than a central portion of the plurality of ceramic layers in the second direction. Multilayer ceramic capacitor.

3. 3. The multilayer ceramic capacitor according to claim 2, In the plurality of ceramic layers and the side margin portion, the magnesium concentration increases toward the high concentration layer. Multilayer ceramic capacitor.

4. 4. The multilayer ceramic capacitor according to claim 1, The grain size of the ceramic layers is smaller in an area adjacent to the high concentration layer than in a central portion in the second direction. Multilayer ceramic capacitor.

5. 5. The multilayer ceramic capacitor according to claim 1, The internal electrodes are adjacent to the high concentration layer and have an oxidized region containing nickel and magnesium. Multilayer ceramic capacitor.

6. 6. The multilayer ceramic capacitor according to claim 1, The side margin portion has a higher magnesium concentration in a central portion in the second direction than the ceramic layers. Multilayer ceramic capacitor.

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