Multilayer ceramic capacitor

Abstract

To provide a laminated ceramic capacitor capable of improving a pressure resistance characteristic and suppressing reduction in electrostatic capacity.SOLUTION: A laminated ceramic capacitor comprises a laminate, a first side margin part and a second side margin part. The laminate includes a plurality of ceramic layers and a plurality of internal electrodes. The first and second side margin parts contain at least one of manganese and magnesium and silicon. In a case where each of the first and second side margin parts is divided into a first inner region in contact with the laminate and a first outer region, a total concentration of manganese and magnesium in the first outer region is higher than a total concentration of manganese and magnesium in the first inner region and the plurality of ceramic layers, and a concentration of silicon in the first inner region is equal to or higher than a concentration of silicon in the first outer region and higher than a concentration of silicon in the plurality of ceramic layers.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a multilayer ceramic capacitor provided with a side margin portion.

Background Art

[0002] A multilayer ceramic capacitor in which a side margin portion is retrofitted to the side surface of a laminate in which ceramic layers and internal electrodes are laminated is known (see, for example, Patent Document 1). This configuration is advantageous for downsizing and increasing the capacitance of the multilayer ceramic capacitor because the thin side margin portion can reliably protect the side surface of the laminate where the internal electrodes are exposed.

[0003] From the viewpoint of expanding the intersection area of the internal electrodes, it is preferable that the side margin portion is thin. On the other hand, in a multilayer ceramic capacitor, when a high voltage is applied to the internal electrodes, electric strain can occur due to the ferroelectricity of the ceramic layers. When the side margin portion is thin, structural defects such as cracks are likely to occur due to the stress caused by the electric strain, and it is difficult to obtain sufficient withstand voltage characteristics.

[0004] On the other hand, a technique is known in which elements such as Mg and Mn are added to the region located between the internal electrodes and the side surface to promote densification of the ceramics (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, when at least one of Mg or Mn was added to the side margin, the added element diffused into the ceramic layer of the laminate, reducing the dielectric constant of the ceramic layer and potentially decreasing the capacitance of the multilayer ceramic capacitor.

[0007] In view of the above circumstances, the object of the present invention is to provide a multilayer ceramic capacitor that can improve voltage resistance and suppress the decrease in capacitance. [Means for solving the problem]

[0008] To achieve the above objective, a multilayer ceramic capacitor according to one embodiment of the present invention comprises a laminate, a first side margin portion and a second side margin portion. The laminate comprises a plurality of ceramic layers stacked in the first axial direction and a plurality of internal electrodes disposed between the plurality of ceramic layers. The positions of the ends of the plurality of internal electrodes in the second axial direction perpendicular to the first axis are aligned with each other within a range of 0.5 μm in the second axial direction. The first side margin portion and the second side margin portion contain at least one of manganese or magnesium and silicon, and are opposite each other in the second axial direction with respect to the laminate. When the first side margin portion and the second side margin portion are each divided in the direction of the second axis into a first inner region in contact with the laminate and a first outer region, The total concentration of manganese and magnesium in the first outer region is higher than the total concentration of manganese and magnesium in the first inner region, and also higher than the total concentration of manganese and magnesium in the multiple ceramic layers. The silicon concentration in the first inner region is greater than or equal to the silicon concentration in the first outer region, and is also greater than the silicon concentration in the multiple ceramic layers.

[0009] In the above configuration, the first outer region contains a high concentration of manganese and / or magnesium, which promotes grain refinement and densification of the ceramics in the first outer region. Furthermore, because the first inner region contains a higher concentration of silicon than the ceramic layer, the glass phase is more easily precipitated in the first inner region. As a result, a first side margin and a second side margin are obtained, each comprising a first inner region with high flexibility and a first outer region with high mechanical strength. Therefore, when a high voltage is applied to the ceramic layer and mechanical deformation (electrostriction) occurs due to the piezoelectric effect, the first inner region releases the stress caused by the electrostriction, and the first outer region can further suppress structural defects such as cracks caused by this stress. As a result, the breakdown voltage characteristics of the multilayer ceramic capacitor can be improved. Furthermore, since the combined concentration of manganese and magnesium in the first inner region is lower than that in the first outer region, the diffusion of manganese and / or magnesium into the ceramic layer is suppressed. This suppresses the decrease in the dielectric constant of the ceramic layer and thus suppresses the decrease in the capacitance of the multilayer ceramic capacitor.

[0010] The silicon concentration in the first inner region may be higher than the silicon concentration in the first outer region. This relatively reduces the silicon concentration in the first outer region, thereby suppressing the precipitation of the glass phase in the first outer region. Consequently, the wear resistance of the surface of the first outer region is improved, and cosmetic defects such as scratches can be suppressed.

[0011] For example, the dimensions of the first side margin portion and the second side margin portion in the second axial direction may be 13 μm or less. This makes it possible to miniaturize and increase the capacitance of multilayer ceramic capacitors. Furthermore, by having the first side margin and the second side margin each include the first inner region and the second inner region of the above configuration, it is possible to make the first side margin and the second side margin thin while reducing the effect of stress due to electrostriction and obtaining a multilayer ceramic capacitor with high breakdown voltage characteristics.

[0012] The above laminate is A capacitance forming section including the above-mentioned multiple ceramic layers and the above-mentioned multiple internal electrodes, It may include at least one of manganese or magnesium, and silicon, and may have a first cover portion and a second cover portion that face each other in the first axial direction with respect to the volume forming portion. When the first cover portion and the second cover portion are each divided into two equal parts in the first axial direction, and partitioned into a second inner region in contact with the volume forming portion and a second outer region, The total concentration of manganese and magnesium in the second outer region is higher than the total concentration of manganese and magnesium in the second inner region, and also higher than the total concentration of manganese and magnesium in the multiple ceramic layers. The silicon concentration in the second inner region is equal to or greater than the silicon concentration in the second outer region, and may also be higher than the silicon concentration in the plurality of ceramic layers.

[0013] In the above configuration, the second outer region contains a high concentration of manganese and / or magnesium, which promotes grain refinement and densification of the ceramics in the second outer region. Therefore, the wear resistance of the surface of the second outer region can be increased, and appearance defects such as scratches can be suppressed. Furthermore, because the combined concentration of manganese and magnesium in the second inner region is lower than in the second outer region, the diffusion of manganese and / or magnesium into the ceramic layer is suppressed. This suppresses the decrease in the dielectric constant of the ceramic layer and thus suppresses the decrease in the capacitance of the multilayer ceramic capacitor. Furthermore, with the above configuration, the distribution of manganese, magnesium, and silicon in the first and second cover portions can be made to correspond to the distribution of manganese, magnesium, and silicon in the first and second side margin portions. This makes the sintering behavior of the first and second cover portions closer to that of the first and second side margin portions, thereby suppressing the generation of stress during sintering. Consequently, structural defects such as cracks caused by such stress can be suppressed. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a multilayer ceramic capacitor capable of improving pressure resistance characteristics and suppressing a decrease in capacitance.

Brief Description of the Drawings

[0015] [Figure 1] It is a perspective view of a multilayer ceramic capacitor according to a first embodiment of the present invention. [Figure 2] It is a cross-sectional view of the multilayer ceramic capacitor taken along line A-A' in FIG. 1. [Figure 3] It is a cross-sectional view of the multilayer ceramic capacitor taken along line B-B' in FIG. 1. [Figure 4] It is a flowchart showing a method for manufacturing the multilayer ceramic capacitor. [Figure 5] It is a perspective view showing a manufacturing process of the multilayer ceramic capacitor. [Figure 6] It is a perspective view showing a manufacturing process of the multilayer ceramic capacitor. [Figure 7] It is a perspective view showing a manufacturing process of the multilayer ceramic capacitor. [Figure 8] It is a cross-sectional view of a multilayer ceramic capacitor according to a second embodiment of the present invention.

Modes for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The X-axis, Y-axis, and Z-axis shown in the drawings are orthogonal to each other and define a coordinate system to which the multilayer ceramic capacitor 10 belongs.

[0017] <First Embodiment> Figures 1 to 3 show a multilayer ceramic capacitor 10 according to a first embodiment of the present invention. Figure 1 is a perspective view of the multilayer ceramic capacitor 10. Figure 2 is a cross-sectional view of the multilayer ceramic capacitor 10 along the line A-A' in Figure 1. Figure 3 is a cross-sectional view of the multilayer ceramic capacitor 10 along the line B-B' in Figure 1.

[0018] The multilayer ceramic capacitor 10 comprises a ceramic body 11, a first external electrode 14, and a second external electrode 15. The ceramic body 11 is configured as a substantially hexahedron having a first end face and a second end face perpendicular to the X-axis direction, a first side face and a second side face perpendicular to the Y-axis direction, and a first main face and a second main face perpendicular to the Z-axis direction. The edges connecting each face of the ceramic body 11 are, for example, rounded.

[0019] The multilayer ceramic capacitor 10 has, for example, the following dimensions: The maximum dimension of the multilayer ceramic capacitor 10 in the X-axis direction is, for example, 0.2 mm or more and 3.5 mm or less. The maximum dimension of the multilayer ceramic capacitor 10 in the Y-axis direction is, for example, 0.1 mm or more and 2.8 mm or less. The maximum dimension of the multilayer ceramic capacitor 10 in the Z-axis direction is, for example, 0.1 mm or more and 2.8 mm or less.

[0020] Each external electrode 14, 15 covers the end face of the ceramic body 11 and faces the ceramic body 11 in the X-axis direction. The external electrodes 14, 15 shown in Figure 1 extend from the end face of the ceramic body 11 to the main surface and side surface. Note that the shape of the external electrodes 14, 15 is not limited to the example shown in Figure 1.

[0021] The external electrodes 14 and 15 are formed from a good electrical conductor. Examples of good electrical conductors forming the external electrodes 14 and 15 include metals or alloys mainly composed of copper (Cu), nickel (Ni), tin (Sn), palladium (Pd), platinum (Pt), silver (Ag), and gold (Au).

[0022] The ceramic body 11 includes a laminate 16, a first side margin portion 17a, and a second side margin portion 17b. The first side margin portion 17a and the second side margin portion 17b face each other in the Y-axis direction with the laminate 16 in between. The first side margin portion 17a and the second side margin portion 17b each cover the laminate 16 from the Y-axis direction.

[0023] The laminate 16 has a first side surface S1 and a second side surface S2 that are perpendicular to the Y-axis direction. The first side surface S1 and the second side surface S2 extend along the Z-axis direction and the X-axis direction, respectively. Furthermore, the laminate 16 has a first end face and a second end face that are perpendicular to the X-axis direction, and a first main face and a second main face that are perpendicular to the Z-axis direction, and is configured as a substantially hexahedron.

[0024] The laminate 16 comprises a plurality of ceramic layers 20 stacked in the Z-axis direction, and a plurality of first internal electrodes 12 and second internal electrodes 13 arranged between the plurality of ceramic layers 20. The ceramic layers 20 are configured as flat plates extending along the XY plane. The internal electrodes 12 and 13 are configured as sheets extending along the XY plane and are arranged alternately along the Z-axis direction. In other words, the internal electrodes 12 and 13 face each other in the Z-axis direction with the ceramic layers 20 in between. The number of layers of internal electrodes 12 and 13 is not limited to the illustrated example, and may be, for example, 30 or more layers.

[0025] The first internal electrode 12 is drawn out to the end face covered by the first external electrode 14. On the other hand, the second internal electrode 13 is drawn out to the end face covered by the second external electrode 15. As a result, the first internal electrode 12 is connected only to the first external electrode 14, and the second internal electrode 13 is connected only to the second external electrode 15.

[0026] With this configuration, when a voltage is applied between the first external electrode 14 and the second external electrode 15 in the multilayer ceramic capacitor 10, a voltage is applied to the multiple ceramic layers 20 between the first internal electrode 12 and the second internal electrode 13. As a result, the multilayer ceramic capacitor 10 stores a charge corresponding to the voltage between the first external electrode 14 and the second external electrode 15.

[0027] In the laminate 16, the portion containing multiple ceramic layers 20 and multiple internal electrodes 12, 13 functions as a capacitance forming portion 18. In addition, the laminate 16 has a first cover portion 19a and a second cover portion 19b that face each other in the Z-axis direction, sandwiching the capacitance forming portion 18. The first cover portion 19a and the second cover portion 19b each cover the capacitance forming portion 18 from the Z-axis direction.

[0028] In the ceramic body 11, high dielectric ceramics are used to increase the capacitance of each ceramic layer 20 between the internal electrodes 12 and 13. Examples of high dielectric ceramics include perovskite materials containing barium (Ba) and titanium (Ti), such as barium titanate (BaTiO3).

[0029] Furthermore, the ceramic body 11 may be composed of a composition system such as strontium titanate (SrTiO3), calcium titanate (CaTiO3), magnesium titanate (MgTiO3), calcium zirconate (CaZrO3), calcium zirconate titanate (Ca(Zr,Ti)O3), barium zirconate (BaZrO3), or titanium dioxide (TiO2).

[0030] In addition to the main components mentioned above, the ceramic layer 20 may contain at least one element from manganese (Mn), magnesium (Mg), or silicon (Si). Mn, Mg, and Si all have the effect of improving sinterability; for example, Mn and Mg contribute to grain refinement and densification of the ceramics. On the other hand, excess amounts of Mn and Mg have the effect of lowering the dielectric constant. For this reason, the total concentration of Mn and Mg and the concentration of Si in the ceramic layer 20 are appropriately determined, taking into consideration the sinterability of the ceramic layer 20 and the design value of the capacitance of the multilayer ceramic capacitor 10, respectively.

[0031] The cover portions 19a and 19b are also formed of insulating ceramics, preferably dielectric ceramics with a composition similar to that of the ceramic layer 20. This makes it possible to suppress the generation of stress caused by the difference in physical properties between the laminate 16 and the cover portions 19a and 19b.

[0032] The thickness of each ceramic layer 20 in the Z-axis direction is, for example, 1.0 μm or less, and may be even less than 0.5 μm, from the viewpoint of increasing capacitance. The thickness of the ceramic layer 20 can be the average value of the thickness measured at multiple locations on the ceramic layer 20. As an example, six layers of ceramic layer 20 are selected from the field of view observed by a scanning electron microscope, and the thickness of each layer is measured at five locations. The average value of the obtained 30 thicknesses can then be taken as the thickness of the ceramic layer 20.

[0033] The internal electrodes 12 and 13 are formed from a good electrical conductor. Typical good electrical conductors forming the internal electrodes 12 and 13 include nickel (Ni), but other examples include metals or alloys mainly composed of copper (Cu), palladium (Pd), platinum (Pt), silver (Ag), and gold (Au).

[0034] The thickness of each internal electrode 12, 13 in the Z-axis direction may be, for example, 0.4 μm or less, from the viewpoint of increasing capacitance by multi-layering the capacitance forming section 18. The thickness of the internal electrodes 12, 13 can be the average value of the thickness measured at multiple locations on the internal electrodes 12, 13. As an example, six layers of internal electrodes 12, 13 in the field of view observed by a scanning electron microscope are selected, and the thickness of five locations in each layer is measured. The average value of the obtained 30 thicknesses can then be taken as the thickness of the internal electrodes 12, 13.

[0035] The internal electrodes 12 and 13 are formed across the entire width of the capacitance forming portion 18 in the Y-axis direction and are exposed on the sides S1 and S2 of the laminate 16. The ends of these internal electrodes 12 and 13 are aligned with each other within a range of 0.5 μm in the Y-axis direction. The first side margin portion 17a covers the first side surface S1 of the laminate 16, and the second side margin portion 17b covers the second side surface S2 of the laminate 16. This ensures insulation between the internal electrodes 12 and 13 on both sides S1 and S2 of the laminate 16.

[0036] [Detailed configuration of the side margin section] Each side margin portion 17a, 17b is formed of insulating ceramics, preferably dielectric ceramics with a composition system similar to that of the ceramic layer 20. This makes it possible to suppress the generation of stress caused by the difference in physical properties between the laminate 16 and the side margin portions 17a, 17b. Furthermore, in this embodiment, each side margin portion 17a, 17b includes at least one of manganese (Mn) or magnesium (Mg) and silicon (Si).

[0037] The first side margin portion 17a and the second side margin portion 17b can be formed thinly because they are added to the laminate 16 afterwards, as will be described later. For example, the dimensions of the first side margin portion 17a and the second side margin portion 17b in the Y-axis direction are 13 μm or less. This ensures sufficient intersection area for the internal electrodes 12 and 13, enabling miniaturization and increased capacitance of the multilayer ceramic capacitor 10. The dimensions of each side margin portion 17a and 17b in the Y-axis direction are the maximum dimensions of each side margin portion 17a and 17b in the Y-axis direction.

[0038] When a voltage is applied to the ceramic layers 20 of the laminate 16 via external electrodes 14 and 15, mechanical deformation (electrostriction) occurs in each ceramic layer 20 to which the voltage is applied due to the piezoelectric effect. When the side margins 17a and 17b become thinner, the proportion occupied by the capacitance forming portion 18 in the ceramic body 11 becomes relatively larger. As a result, large stresses are generated in the side margins 17a and 17b due to electrostriction, which can lead to structural defects such as cracks.

[0039] In response to this, it is conceivable to add at least one of manganese (Mn) or magnesium (Mg) as a sintering aid to the side margin portions 17a and 17b to refine the crystal grains of the side margin portions 17a and 17b and increase the density of the ceramics. This can improve the mechanical strength of the side margin portions 17a and 17b and suppress structural defects caused by electrostriction.

[0040] On the other hand, if the Mn and / or Mg added in large quantities to the side margin portions 17a and 17b diffuse into the ceramic layer 20, the dielectric constant of the ceramic layer 20 may decrease, which can reduce the capacitance of the multilayer ceramic capacitor 10.

[0041] Therefore, in this embodiment, the first side margin portion 17a and the second side margin portion 17b are each divided in the Y-axis direction into a first inner region R11 and a first outer region R12 that are in contact with the laminate 16, and the composition of each region is adjusted as follows to suppress structural defects due to electrostriction and suppress the decrease in capacitance.

[0042] The first inner region R11 and the first outer region R12 are defined by a virtual plane that bisects the central portions of each side margin portion 17a and 17b in the X-axis and Z-axis directions in the Y-axis direction. This virtual plane is parallel to the XZ plane. In other words, the dimensions in the Y-axis direction at the central portions of the first inner region R11 in the X-axis and Z-axis directions are equal to the dimensions in the Y-axis direction at the central portions of the first outer region R12 in the X-axis and Z-axis directions. The elemental concentrations in each region can be obtained, for example, by quantitative measurement using an electron probe microanalyzer (EPMA).

[0043] The combined concentration of Mn and Mg in the first outer region R12 is higher than the combined concentration of Mn and Mg in the first inner region R11, and also higher than the combined concentration of Mn and Mg in the multiple ceramic layers 20. This promotes grain refinement and ceramic densification in the first outer region R12, potentially improving the mechanical strength of the first outer region R12. Note that the first outer region R12 may contain only Mn or only Mg.

[0044] On the other hand, the Si concentration in the first inner region R11 is greater than or equal to the Si concentration in the first outer region R12, and is also higher than the Si concentration in the multiple ceramic layers 20. Si in ceramics can be precipitated as a glass phase by sintering. Having such a Si concentration in the first inner region R11 imparts flexibility to the first inner region R11 through a relatively soft glass phase.

[0045] As a result, when stress is applied to the side margin portions 17a and 17b due to electrostriction, this stress is released by the flexible first inner region R1, and structural defects such as cracks are prevented by the first outer region R12, which has high mechanical strength. Therefore, even when a high voltage is applied to the multilayer ceramic capacitor 10, structural defects in the side margin portions 17a and 17b are effectively prevented, and the breakdown voltage characteristics of the multilayer ceramic capacitor 10 are improved.

[0046] Furthermore, in the first outer region R12, the density is increased by Mn and / or Mg, thereby improving the surface wear resistance. This suppresses scratches and other damage caused by handling, and reduces defects in the appearance of the multilayer ceramic capacitor 10.

[0047] Furthermore, because the total concentration of Mn and Mg in the first inner region R11 becomes relatively low, the diffusion of Mn and / or Mg into the ceramic layer 20 is suppressed. As a result, the decrease in the dielectric constant of the ceramic layer 20 is suppressed, and the decrease in the capacitance of the multilayer ceramic capacitor 10 is suppressed.

[0048] The Si concentration in the side margin regions 17a and 17b may be uniform, for example. That is, the Si concentration in the first inner region R11 may be the same as the Si concentration in the first outer region R12.

[0049] Alternatively, the Si concentration in the first inner region R11 may be higher than the Si concentration in the first outer region R12. This relatively reduces the Si concentration in the first outer region R12, suppressing the deposition of the glass phase in the first outer region R12. Consequently, the wear resistance of the surface of the first outer region R12 is further enhanced, and defects in the appearance of the multilayer ceramic capacitor 10 are more effectively suppressed.

[0050] [Manufacturing method for multilayer ceramic capacitor 10] Figure 4 is a flowchart showing the manufacturing method of the multilayer ceramic capacitor 10. Figures 5 to 7 schematically show the manufacturing process of the multilayer ceramic capacitor 10. The manufacturing method of the multilayer ceramic capacitor 10 will be explained below in accordance with Figure 4, with reference to Figures 5 to 7 as appropriate.

[0051] (Step S01: Laminate fabrication) In step S01, an unfired laminate 116 is produced by laminating and cutting a first ceramic sheet 101 and a second ceramic sheet 102 for forming the volume forming section 18, and a third ceramic sheet 103 for forming the cover sections 19a and 19b.

[0052] The ceramic sheets 101, 102, and 103 shown in Figure 5 are composed of unfired ceramic green sheets mainly made of dielectric ceramics. The ceramic sheets 101, 102, and 103 are formed into sheets using, for example, a roll coater or a doctor blade. The thickness of the ceramic sheets 101 and 102 is adjusted according to the thickness of the ceramic layer 20 after firing. The thickness of the third ceramic sheet 103 can be adjusted as appropriate.

[0053] An unfired first internal electrode 112 corresponding to the first internal electrode 12 is formed on the first ceramic sheet 101. An unfired second internal electrode 113 corresponding to the second internal electrode 13 is formed on the second ceramic sheet 102. No internal electrodes are formed on the third ceramic sheet 103.

[0054] Each internal electrode 112, 113 has multiple strip-shaped electrode patterns that cross a cutting line Lx parallel to the X-axis direction and extend along a cutting line Ly parallel to the Y-axis direction. These internal electrodes 112, 113 are formed by applying a conductive paste to ceramic sheets 101, 102 using methods such as screen printing or gravure printing.

[0055] As shown in Figure 5, ceramic sheets 101 and 102 are stacked alternately in the Z-axis direction. The stack of ceramic sheets 101 and 102 corresponds to the volume-forming section 18. Ceramic sheet 103 is stacked on the upper and lower surfaces of the stack of ceramic sheets 101 and 102 in the Z-axis direction. The stack of ceramic sheets 103 corresponds to the cover sections 19a and 19b. The number of layers of ceramic sheets 101, 102, and 103 can be adjusted as needed.

[0056] Next, the laminate of ceramic sheets 101, 102, and 103 is pressed together from the Z-axis direction and cut along the cutting lines Lx and Ly. For cutting the laminate, for example, a push-cut blade or a rotary blade can be used. This produces the laminate 116 shown in Figure 6.

[0057] As shown in Figure 6, the laminate 116 has an unfired capacitance forming portion 118 on which unfired internal electrodes 112 and 113 are formed, an unfired first cover portion 119a, and an unfired second cover portion 119b. The laminate 116 has a first side surface S1 and a second side surface S2 perpendicular to the Y-axis direction, a first end surface and a second end surface perpendicular to the X-axis direction, and a first main surface and a second main surface perpendicular to the Z-axis direction. The first side surface S1 and the second side surface S2 are cross-sections corresponding to the cutting line Lx. The first end surface and the second end surface are cross-sections corresponding to the cutting line Ly. The ends of the unfired internal electrodes 112 and 113 are exposed from the first side surface S1 and the second side surface S2.

[0058] (Step S02: Formation of side margins) In step S02, an unfired first side margin portion 117a is provided on the first side surface S1 of the laminate 116 obtained in step S01, and an unfired second side margin portion 117b is provided on the second side surface S2. As a result, as shown in Figure 7, an unfired ceramic body 111 is obtained in which the sides S1 and S2, where the internal electrodes 112 and 113 are exposed, are covered by the side margin portions 117a and 117b.

[0059] In this embodiment, the first side margin portion 117a and the second side margin portion 117b each include a first inner layer Ru1 and a first outer layer Ru2. The first inner layer Ru1 is a layer in contact with the laminate 116. The first outer layer Ru2 is a layer positioned outside the first inner layer Ru1 in the Y-axis direction. The first inner layer Ru1 and the first outer layer Ru2 are each formed from unfired ceramic sheets or ceramic slurries of different compositions. The thicknesses of the first inner layer Ru1 and the first outer layer Ru2 in the Y-axis direction are preferably the same, but may be different.

[0060] The first outer layer Ru2 contains at least one of Mn or Mg. The total concentration of Mn and Mg in the first outer layer Ru2 is higher than the total concentration of Mn and Mg in the first inner layer Ru1, and also higher than the total concentration of Mn and Mg in the ceramic sheets 101 and 102. The first inner layer Ru1 contains Si. The Si concentration in the first inner layer Ru1 is greater than or equal to the Si concentration in the first outer layer Ru2, and is also greater than the Si concentration in the ceramic sheets 101 and 102.

[0061] Each of the side margins 117a and 117b may be formed using a ceramic sheet forming the first inner layer Ru1 and a ceramic sheet forming the first outer layer Ru2. For example, the ceramic sheet forming the first inner layer Ru1 may be attached to the sides S1 and S2, and then the ceramic sheet forming the first outer layer Ru2 may be attached on top of the ceramic sheet. Alternatively, a laminated sheet of the ceramic sheet forming the first inner layer Ru1 and the ceramic sheet forming the first outer layer Ru2 may be attached to the sides S1 and S2. As an example, the laminated sheet can be attached to the sides S1 and S2 by pressing the sides S1 and S2 against a large laminated sheet and punching out the laminated sheet with the sides S1 and S2.

[0062] Alternatively, the side margins 117a and 117b may be formed by coating each side surface S1 and S2 with a ceramic slurry that forms the first inner layer Ru1, and then coating the first outer layer Ru2 with a ceramic slurry that forms the first outer layer Ru1. The coating method can be applied by coating or dipping.

[0063] (Step S03: Firing) In step S03, the ceramic body 11 obtained in step S02 is fired to produce the ceramic body 11 of the multilayer ceramic capacitor 10 shown in Figures 1-3. In step S03, the laminate 116 becomes the laminate 16, and the side margin portions 117a and 117b become the side margin portions 17a and 17b.

[0064] In this embodiment, step S03 causes the first inner layer Ru1 of the side margin portions 117a and 117b to become the inner region of the side margin portions 17a and 17b. Similarly, the first outer layer Ru2 becomes the outer region of the side margin portions 17a and 17b. As a result, side margin portions 17a and 17b are formed, including the first inner region R11 and the first outer region R12 with the above-described composition.

[0065] The first outer layer Ru2 has a high total concentration of Mn and Mg, which promotes grain refinement and ceramic densification during firing. Consequently, a first outer region R12 with high mechanical strength is formed. Furthermore, although the Mn and / or Mg in the first outer layer Ru2 may diffuse during firing, the presence of the first inner layer Ru1, which has a low total concentration of Mn and Mg, suppresses the diffusion of Mn and / or Mg into the laminate 116.

[0066] On the other hand, in the first inner layer Ru1, a glass phase precipitates due to the presence of Si. This ensures the flexibility of the first inner region R11 of the side margins 17a and 17b, making it possible to release stress caused by electrostriction.

[0067] The firing temperature in step S03 can be determined based on the sintering temperature of the ceramic body 111. For example, when using a barium titanate (BaTiO3)-based material, the firing temperature can be set to approximately 1000-1300°C. Furthermore, firing can be carried out, for example, under a reducing atmosphere or a low oxygen partial pressure atmosphere.

[0068] (Step S04: External electrode formation) In step S04, the multilayer ceramic capacitor 10 shown in Figures 1-3 is fabricated by forming external electrodes 14 and 15 on both ends of the ceramic substrate 11 obtained in step S03 in the X-axis direction. The method for forming the external electrodes 14 and 15 in step S04 can be arbitrarily selected from known methods.

[0069] As a result, the multilayer ceramic capacitor 10 is completed. In this manufacturing method, side margin portions 117a and 117b are formed on the side surfaces S1 and S2 of the laminate 116 where the internal electrodes 112 and 113 are exposed, so that the positions of the ends of the multiple internal electrodes 12 and 13 in the ceramic body 11 in the Y-axis direction are aligned within a range of 0.5 μm or less.

[0070] [Examples] As an example of the first embodiment, samples of multilayer ceramic capacitors, Examples 1 to 4 and Comparative Examples 1 to 3, were prepared based on the above manufacturing method. In each sample, steps S01 to S04 were performed using a ceramic sheet having a ceramic green sheet mainly composed of barium titanate and internal electrodes made of a conductor containing Ni. The number of layers of the ceramic sheet on which the internal electrodes were formed was 470.

[0071] The dimensions of each sample after firing were approximately 1.0 mm in the X-axis direction, 0.5 mm in the Y-axis direction, and 0.5 mm in the Z-axis direction. The average thickness of the ceramic layer was 0.5 μm, and the average thickness of the internal electrodes was 0.4 μm.

[0072] In each sample, the distribution of Mn or Mg and Si was adjusted by changing the number and composition of the side margin layers. The thickness of the side margin in the Y-axis direction after firing for each sample is as shown in Table 1.

[0073] In the sample of Example 1, a two-layer side margin portion was formed, including a first outer layer and a first inner layer. Mn was added to the first outer layer to a higher concentration than that of the first inner layer and the ceramic layer. Si was added to the first inner layer to a higher concentration than that of the first outer layer and the ceramic layer.

[0074] In the sample of Example 2, a two-layer side margin portion was formed, including a first outer layer and a first inner layer. Mg was added to the first outer layer to a higher concentration than that of the first inner layer and the ceramic layer. Si was added to the first inner layer to a higher concentration than that of the first outer layer and the ceramic layer.

[0075] In the sample of Example 3, a two-layer side margin portion was formed, including a first outer layer and a first inner layer. Mn was added to the first outer layer at a higher concentration than that of the first inner layer and the ceramic layer. Si was added to the first inner layer and the first outer layer at the same concentration, but at a higher concentration than that of the ceramic layer.

[0076] In the sample of Example 4, a two-layer side margin portion was formed, including a first outer layer and a first inner layer. Mg was added to the first outer layer at a higher concentration than that of the first inner layer and the ceramic layer. Si was added to the first inner layer and the first outer layer at the same concentration, but at a higher concentration than that of the ceramic layer.

[0077] In the sample of Comparative Example 1, a single-layer side margin was formed. Mn and Si were added to the side margin so that they were uniformly distributed throughout.

[0078] In the sample of Comparative Example 2, a single-layer side margin was formed. Mn and Si were added to the side margin so that they were uniformly distributed throughout.

[0079] In the sample of Comparative Example 3, a two-layer side margin portion was formed, including a first outer layer and a first inner layer. Mn was added to the first inner layer at a higher concentration than that of the first outer layer and the ceramic layer. Si was added to the first outer layer at a higher concentration than that of the first inner layer and the ceramic layer.

[0080] After firing, each sample was polished up to the center in the X-axis direction so that the YZ cross-section was exposed, and the distribution of Mn, Mg, and Si in the cross-section was evaluated by EPMA mapping analysis. The results are shown in Table 1. In the distribution of each element in Table 1, "inside" means that the element is concentrated in the first inner region of the side margin. "Outside" means that the element is concentrated in the first outer region of the side margin. "Uniform" means that the element is evenly distributed throughout the entire side margin.

[0081] [Table 1]

[0082] The breakdown voltage (BDV) was measured for 50 samples of each example and comparative example, and the average value was calculated as the withstand voltage. The results are shown in Table 1. The breakdown voltage was determined by increasing the voltage applied to each sample at 25°C until breakdown occurred. The withstand voltage was evaluated as follows: 13V or higher was designated as A, 10V or higher but less than 13V as B, and less than 10V as C.

[0083] As shown in Table 1, in Examples 1 to 4, the thickness of the side margin was thin at 13 μm, but in all cases the dielectric strength evaluation was A. On the other hand, in Comparative Examples 2 and 3, where the thickness of the side margin was 13 μm, the dielectric strength evaluation was B and C, respectively. Furthermore, in Comparative Example 1, where the thickness of the side margin was thick at 18 μm, the dielectric strength evaluation was A.

[0084] This revealed that even when the side margin is thin, less than 13 μm, the dielectric strength can be improved by distributing more Mn or Mg in the first outer region and distributing Si uniformly or in the first inner region.

[0085] Next, the capacitance of 50 samples from each example and comparative example was measured, and the average value for each example and comparative example was calculated. The results are shown in Table 1. For capacitance evaluation, values ​​of 12.0 μF or higher were designated as A, values ​​between 10.0 μF and 12.0 μF were designated as B, and values ​​below 10.0 μF were designated as C.

[0086] As shown in Table 1, in Examples 1 to 4, where Mn or Mg was distributed more in the first outer region, the capacitance evaluation was A in all cases. On the other hand, in Comparative Examples 1 and 2, which had a uniform Mn distribution, the capacitance evaluation was B, and in Comparative Example 3, where Mn was distributed more in the first inner region, the evaluation was C. From these results, it was found that by distributing more Mn or Mg in the first outer region, the diffusion of Mn or Mg into the laminate is suppressed, and the decrease in capacitance can be suppressed.

[0087] Next, the presence or absence of appearance defects was visually assessed for 200 samples from each example and comparative example. Then, for each example and comparative example, the percentage of samples with appearance defects out of the 200 samples was calculated as the appearance defect rate. The results are shown in Table 1. The appearance defect rate was evaluated as follows: less than 2.0% was A, 2.0% or more and less than 5.0% was B, and 5.0% or more was C.

[0088] As shown in Table 1, the appearance defect rate was evaluated as A in all of Examples 1 to 4. On the other hand, the appearance defect rate was evaluated as B in Comparative Examples 1 and 2, and as C in Comparative Example 3. From these results, it was found that by distributing Mn or Mg in large quantities in the first outer region and Si uniformly or in large quantities in the first inner region, the wear resistance of the side margin portion can be improved and appearance defects can be suppressed.

[0089] From the above, it was found that distributing Mn or Mg in large quantities in the first outer region and uniformly distributing Si or distributing it in large quantities in the first inner region improves withstand voltage and capacitance, and reduces the rate of defects in appearance. Furthermore, from the results of Examples 1 and 2, and Examples 3 and 4, it is considered that Mn and Mg have similar effects on withstand voltage characteristics, capacitance, and wear resistance.

[0090] <Second Embodiment> In the first embodiment, the first inner region R11 and the first outer region R12 of the side margin portions 17a and 17b had a predetermined elemental distribution, but in addition, the cover portions 39a and 39b may also have a similar elemental distribution. In the following embodiments, similar components to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0091] Figure 8 is a cross-sectional view showing a multilayer ceramic capacitor 30 according to a second embodiment of the present invention, and is a cross-section at the same position as in Figure 3. The multilayer ceramic capacitor 30 comprises a ceramic body 31 different from that of the first embodiment, and a first external electrode 14 and a second external electrode 15 similar to those of the first embodiment. Note that the external electrodes 14 and 15 are not shown in Figure 8.

[0092] The ceramic body 31 has a laminate 36 that is different from that of the first embodiment, and a first side margin portion 17a and a second side margin portion 17b that are the same as those of the first embodiment. The laminate 36 includes a volume-forming portion 18 similar to that of the first embodiment, and a first cover portion 39a and a second cover portion 39b that differ from those of the first embodiment.

[0093] Each cover portion 39a, 39b is formed of an insulating ceramic, preferably a dielectric ceramic with a composition system similar to that of the ceramic layer 20. Furthermore, in this embodiment, each cover portion 39a, 39b contains at least one of manganese (Mn) or magnesium (Mg) and silicon (Si).

[0094] In this embodiment, the first cover portion 39a and the second cover portion 39b are each divided into two equal parts in the Z-axis direction to form a second inner region R21 and a second outer region R22 that are in contact with the volume forming portion 18, and the composition of each region is adjusted. The second inner region R21 and the second outer region R22 are defined by a virtual plane that bisects the central portions of each cover portion 39a and 39b in the X-axis and Y-axis directions in the Z-axis direction. This virtual plane is parallel to the XY plane. In other words, the dimensions in the Z-axis direction at the central portions of the second inner region R21 in the X-axis and Y-axis directions are equal to the dimensions in the Z-axis direction at the central portions of the second outer region R22 in the X-axis and Y-axis directions.

[0095] The total concentration of Mn and Mg in the second outer region R22 is higher than, for example, the total concentration of Mn and Mg in the second inner region R21, and higher than the total concentration of Mn and Mg in the multiple ceramic layers 20. This promotes grain refinement and ceramic densification in the second outer region R22, improving surface wear resistance. Therefore, cosmetic defects of the multilayer ceramic capacitor 10 caused by scratches during handling are more effectively suppressed.

[0096] Furthermore, because the total concentration of Mn and Mg in the second inner region R21 becomes relatively low, the diffusion of Mn and / or Mg into the ceramic layer 20 is suppressed. As a result, the decrease in the dielectric constant of the ceramic layer 20 is suppressed, and the decrease in the capacitance of the multilayer ceramic capacitor 30 is suppressed.

[0097] Furthermore, the Si concentration in the second inner region R21 is, for example, greater than or equal to the Si concentration in the second outer region R22, and is also greater than the Si concentration in the multiple ceramic layers 20.

[0098] With the above configuration, the distribution of Mn, Mg, and Si in the second inner region R21 and the second outer region R22 can be made to correspond to the distribution of Mn, Mg, and Si in the first inner region R11 and the first outer region R12 of the side margin portions 17a and 17b. As described above, the distribution of each of the above elements can affect the sintering behavior of each region. Therefore, with the above configuration, the sintering behavior of the cover portions 39a and 39b can be made to approximate the sintering behavior of the side margin portions 17a and 17b, and the stress generated between the cover portions 39a and 39b and the side margin portions 17a and 17b can be reduced. Thus, structural defects such as cracks due to sintering can be suppressed.

[0099] The first cover portion 39a and the second cover portion 39b of this embodiment are formed, for example, by laminating ceramic sheets of different compositions.

[0100] Specifically, each unfired cover portion 39a, 39b includes a second inner layer and a second outer layer. The second inner layer is a layer adjacent to the volume-forming portion. The second outer layer is a layer laminated on the Z-axis side of the second inner layer. The second inner layer and the second outer layer may each be composed of a single ceramic sheet or multiple ceramic sheets.

[0101] The second outer layer contains at least one of Mn or Mg. The total concentration of Mn and Mg in the second outer layer is higher than the total concentration of Mn and Mg in the ceramic sheet constituting the second inner layer and the ceramic layer 20. The second inner layer contains Si. The Si concentration in the second inner layer is greater than or equal to the Si concentration in the second outer layer, and is also greater than the Si concentration in the ceramic sheet constituting the ceramic layer 20.

[0102] Since each unfired cover portion 39a, 39b includes the second inner layer and the second outer layer of the above configuration, cover portions 39a, 39b including the second inner region R21 and the second outer region R22 can be formed after firing.

[0103] <Other Embodiments> Although various embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the present invention.

[0104] For example, in the first embodiment, it was explained that each of the unfired side margin portions 117a and 117b contains a first inner layer Ru1 and a first outer layer Ru2 with different compositions, but this is not limited to this. For example, each of the unfired side margin portions 117a and 117b may contain three or more layers such that the total concentration of Mn and Mg increases toward the outside. In this case, the three or more layers may have the same Si concentration, or a Si concentration that increases toward the inside. This also makes it possible to form side margin portions 17a and 17b containing a first inner region R11 and a first outer region R12 with the above composition after firing.

[0105] Similarly, in the second embodiment, each of the unfired cover portions 39a and 39b may contain three or more layers such that the total concentration of Mn and Mg increases toward the outside. In this case, the three or more layers may have a uniform Si concentration or a Si concentration that increases toward the inside. [Explanation of Symbols]

[0106] 10,30… Multilayer ceramic capacitor 12,13…Internal electrode 16, 36... Laminate 17a...First side margin section 17b...Second side margin section 18...Capacity forming part 20…Ceramic layer 19a, 39a... First cover section 19b, 39b... Second cover section R11...first inner area R12...first outer area

Claims

1. A laminate comprising a plurality of ceramic layers stacked in a first axial direction, and a plurality of internal electrodes disposed between the plurality of ceramic layers, wherein the positions of the ends of the plurality of internal electrodes in a second axial direction perpendicular to the first axis are aligned with each other within a range of 0.5 μm in the second axial direction, A first side margin portion and a second side margin portion are located opposite each other in the second axial direction, comprising manganese or magnesium and silicon, with respect to the laminate. It is equipped with, When the first side margin portion and the second side margin portion are each divided into three equal parts in the second axial direction, and are partitioned into a first inner region in contact with the laminate, a first central region, and a first outer region, The total concentration of manganese and magnesium in the first outer region is higher than the total concentration of manganese and magnesium in the first central region, the total concentration of manganese and magnesium in the first central region is higher than the total concentration of manganese and magnesium in the first inner region, and the total concentration of manganese and magnesium in the first outer region is higher than the total concentration of manganese and magnesium in the plurality of ceramic layers. The manganese concentration in the first outer region is higher than the manganese concentration in the first inner region, and the magnesium concentration in the first outer region is higher than the magnesium concentration in the first inner region. The silicon concentration in the first inner region is greater than or equal to the silicon concentration in the first central region, the silicon concentration in the first central region is greater than or equal to the silicon concentration in the first outer region, and the silicon concentration in the first inner region is higher than the silicon concentration in the plurality of ceramic layers. Multilayer ceramic capacitor.

2. A multilayer ceramic capacitor according to claim 1, The silicon concentration in the first inner region is higher than the silicon concentration in the first central region, and the silicon concentration in the first central region is higher than the silicon concentration in the first outer region. Multilayer ceramic capacitor.

3. A multilayer ceramic capacitor according to claim 1 or 2, The dimensions of the first side margin portion and the second side margin portion in the second axial direction are 13 μm or less. Multilayer ceramic capacitor.

4. A multilayer ceramic capacitor according to any one of claims 1 to 3, The laminated body is A capacitance forming section comprising the plurality of ceramic layers and the plurality of internal electrodes, It comprises manganese or magnesium, and silicon, and has a first cover portion and a second cover portion that face each other in the first axial direction with respect to the volume forming portion, When the first cover portion and the second cover portion are each divided into three equal parts in the first axial direction, and are partitioned into a second inner region in contact with the volume forming portion, a second central region, and a second outer region, The total concentration of manganese and magnesium in the second outer region is higher than the total concentration of manganese and magnesium in the second central region, the total concentration of manganese and magnesium in the second central region is higher than the total concentration of manganese and magnesium in the second inner region, and the total concentration of manganese and magnesium in the first outer region is higher than the total concentration of manganese and magnesium in the plurality of ceramic layers. The manganese concentration in the second outer region is higher than the manganese concentration in the second inner region, and the magnesium concentration in the second outer region is higher than the magnesium concentration in the second inner region. The silicon concentration in the second inner region is greater than or equal to the silicon concentration in the second central region, the silicon concentration in the second central region is greater than or equal to the silicon concentration in the second outer region, and the silicon concentration in the second inner region is higher than the silicon concentration in the plurality of ceramic layers. Multilayer ceramic capacitor.

5. A multilayer ceramic capacitor according to any one of claims 1 to 4, The thickness of each of the plurality of internal electrodes in the first axial direction is 0.4 μm or less. Multilayer ceramic capacitor.

6. A multilayer ceramic capacitor according to claim 1, The silicon concentration in the first inner region is the same as the silicon concentration in the first central region and the silicon concentration in the first outer region, and is higher than the silicon concentration in the plurality of ceramic layers. The first inner region has a uniform silicon concentration throughout its entire area, the first central region has a uniform silicon concentration throughout its entire area, and the first outer region has a uniform silicon concentration throughout its entire area. Multilayer ceramic capacitor.

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