Multilayer ceramic capacitor
The multilayer ceramic capacitor design addresses crack issues by incorporating non-existent regions at the corners to mitigate stress concentration, ensuring reliable and strong connections in high-profile capacitors.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TAIYO YUDEN KK
- Filing Date
- 2022-06-23
- Publication Date
- 2026-06-23
AI Technical Summary
The diffusion of Cu from external electrodes into internal electrodes in multilayer ceramic capacitors leads to expansion and stress concentration at the corners, increasing the likelihood of cracks, particularly in high-profile capacitors with many stacked internal electrodes, which affects long-term reliability and connection strength.
A multilayer ceramic capacitor design with alternating internal electrodes and external electrodes, featuring non-existent regions at the corners to alleviate stress concentration, preventing cracks by ensuring internal electrodes are absent near the corners.
The design effectively suppresses crack formation at the corners of the ceramic body, enhancing long-term reliability and connection strength while maintaining high capacitance.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a high-profile multilayer ceramic capacitor.
Background Art
[0002] Patent Document 1 describes a phenomenon in which, when an external electrode mainly composed of Cu is baked on a ceramic body having an internal electrode mainly composed of Ni, Cu in the external electrode diffuses into the internal electrode while reacting with Ni. Due to this phenomenon, in the ceramic body, expansion occurs at the end portion of the internal electrode close to the external electrode.
[0003] In the ceramic body, only the region close to the external electrode tends to expand in the stacking direction due to such expansion of the internal electrode. In the ceramic body, the internal stress generated thereby concentrates at the corners, making cracks more likely to occur. The occurrence of such cracks is more prominent in a high-profile ceramic body with a large number of stacked internal electrodes.
[0004] In a multilayer ceramic capacitor, in order to suppress the diffusion of Cu in the external electrode into the internal electrode, it is effective to lower the baking temperature of the external electrode with respect to the ceramic body. That is, by lowering the baking temperature, the reaction rate between Cu and Ni decreases, so that the diffusion of Cu into the internal electrode can be suppressed.
Prior Art Documents
Patent Documents
[0005]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0006] However, lowering the sintering temperature of the external electrodes onto the ceramic body makes it difficult to achieve sufficient sinterability of the external electrodes. As a result, multilayer ceramic capacitors are more prone to problems such as reduced long-term reliability due to decreased density of the external electrodes and insufficient connection strength of the external electrodes to the ceramic body.
[0007] In view of the above circumstances, the object of the present invention is to suppress the occurrence of cracks in tall ceramic bodies. [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 ceramic body and first and second external electrodes. The ceramic body is stacked alternately along a first axis and is drawn out to first and second end faces perpendicular to a second axis perpendicular to the first axis, respectively, and comprises an electrode stack having a plurality of first and second internal electrodes mainly composed of Ni, and a pair of cover parts that cover the electrode stack from both sides in the first axis direction and constitute first and second main surfaces perpendicular to the first axis, wherein the dimension in the first axis direction is 1.5 times or more the dimension in the third axis direction perpendicular to the first and second axes. Each of the above-mentioned plurality of first and second external electrodes has first and second end-face covering portions that cover the first and second end faces, and first and second extension portions that extend from the first and second end-face covering portions to the first and second main faces, and is mainly composed of Cu. The plurality of first and second internal electrodes described above consist of a plurality of first and second inner layer internal electrodes having a common rectangular planar shape, and at least one of the four corners of the plurality of first and second inner layer internal electrodes. Corner portions on the first and second end faces as described above The first and second non-existent regions are located at the positions corresponding to each It consists of a plurality of first and second outer layer internal electrodes provided. In the second axial direction described above, the dimension in the third axial direction of the region on the first end face side of the first outer layer internal electrode is smaller than the dimension in the third axial direction of the central region of the first outer layer internal electrode by the dimension of the first absent region at the corner on the first end face side. In the second axial direction described above, the dimension in the third axial direction of the region on the second end face side of the second outer layer internal electrode is smaller than the dimension in the third axial direction of the central region of the second outer layer internal electrode by the dimension of the second absent region at the corner on the second end face side. The electrode stacking portion comprises a pair of outer layer portions adjacent to the pair of cover portions, on which the plurality of first and second outer layer internal electrodes are stacked, and an inner layer portion located between the pair of outer layer portions, on which the plurality of first and second inner layer internal electrodes are stacked.
[0009] In this multilayer ceramic capacitor, the pattern of the inner electrodes of the outer layer, which are stacked in the outer layer, is different from that of the inner electrodes of the inner layer, which are stacked in the inner layer. This makes it possible to create a region where no internal electrodes are present near the corners of the ceramic body. As a result, even if expansion occurs in the internal electrodes due to the diffusion of Cu in the outer electrodes, stress is less likely to concentrate at the corners of the ceramic body. Therefore, this multilayer ceramic capacitor can prevent the occurrence of cracks at the corners of the ceramic body.
[0010] The plurality of first and second outer layer internal electrodes may have first and second non-existent regions at all positions corresponding to the four corners of the first and second inner layer internal electrodes. The plurality of first outer layer internal electrodes described above may have a planar shape that is narrowed in the third axial direction in the entire region facing the first extension in the first axial direction. The plurality of second outer layer internal electrodes described above may have a planar shape that is narrowed in the third axial direction in the entire region facing the second extension in the first axial direction. In the plurality of first outer layer internal electrodes described above, the dimension in the third axial direction in the region facing the first extension in the first axial direction may be two-thirds or less of the dimension of the plurality of first inner layer internal electrodes. In the plurality of second outer layer internal electrodes described above, the dimension in the third axial direction in the region facing the second extension in the first axial direction may be two-thirds or less of the dimension of the plurality of second inner layer internal electrodes. The plurality of first outer layer internal electrodes described above do not necessarily have to face the second extension in the first axial direction. [Effects of the Invention]
[0011] As described above, according to the present invention, the generation of cracks in the high-profile ceramic body can be suppressed.
Brief Description of the Drawings
[0012] [Figure 1] It is a perspective view of a multilayer ceramic capacitor according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view of the multilayer ceramic capacitor along the line A1 - A1' in FIG. 1. [Figure 3] It is a cross-sectional view of the multilayer ceramic capacitor along the line B1 - B1' in FIG. 1. [Figure 4] It is a cross-sectional view of the multilayer ceramic capacitor along the line A2 - A2' in FIG. 1. [Figure 5] It is a cross-sectional view of the multilayer ceramic capacitor along the line B2 - B2' in FIG. 1. [Figure 6] It is a plan view of the inner layer internal electrode of the multilayer ceramic capacitor. [Figure 7] It is a plan view of the outer layer internal electrode of the multilayer ceramic capacitor. [Figure 8] It is a flowchart showing the manufacturing method of the multilayer ceramic capacitor. [Figure 9] It is a plan view of the inner layer ceramic sheet prepared in step S01. [Figure 10] It is a plan view of the outer layer ceramic sheet prepared in step S01. [Figure 11] It is a plan view of the cover ceramic sheet prepared in step S01. [Figure 12] It is a schematic view showing step S02. [Figure 13] It is a plan view showing step S03. [Figure 14] It is a plan view showing another form of the outer layer internal electrode of the multilayer ceramic capacitor. [Figure 15] It is a plan view showing another form of the outer layer internal electrode of the multilayer ceramic capacitor. [Figure 16]This is a plan view showing another form of the inner electrode of the outer layer of the above multilayer ceramic capacitor. [Modes for carrying out the invention]
[0013] Hereinafter, an embodiment of the multilayer ceramic capacitor 10 of the present invention will be described with reference to the drawings. Note that the drawings show mutually orthogonal X, Y, and Z axes as appropriate. The X, Y, and Z axes define a fixed coordinate system fixed to the multilayer ceramic capacitor 10.
[0014] [Configuration of the multilayer ceramic capacitor 10] Figures 1-3 show a multilayer ceramic capacitor 10 according to one 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 A1-A1' in Figure 1. Figure 3 is a cross-sectional view of the multilayer ceramic capacitor 10 along the line B1-B1' in Figure 1.
[0015] Figures 2 and 3 show longitudinal sections of the region including the central part of the multilayer ceramic capacitor 10. Specifically, Figure 2 shows a cross-section of the central part of the multilayer ceramic capacitor 10 along the XZ plane in the Y-axis direction. Figure 3 shows a cross-section of the central part of the multilayer ceramic capacitor 10 along the YZ plane in the X-axis direction.
[0016] 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 hexahedron having first and second main faces M1 and M2 perpendicular to the Z axis, first and second end faces E1 and E2 perpendicular to the X axis, and a pair of side faces S1 and S2 perpendicular to the Y axis.
[0017] The main surfaces M1, M2, end surfaces E1, E2, and side surfaces S1, S2 of the ceramic body 11 are all configured as flat surfaces. In this embodiment, a flat surface does not have to be strictly planar as long as it is perceived as flat when viewed as a whole, and includes, for example, surfaces having minute irregularities on the surface or gently curved shapes within a predetermined range.
[0018] The multilayer ceramic capacitor 10 has a tall ceramic body 11 whose Z-axis dimension T is 1.5 times or more than its Y-axis dimension W. In other words, the multilayer ceramic capacitor 10 can be mounted in a mounting space limited by the Y-axis while ensuring a large capacitance by increasing the dimension T of the ceramic body 11.
[0019] Furthermore, in the multilayer ceramic capacitor 10, the dimension L in the X-axis direction of the ceramic element 11 only needs to be larger than dimension W, and may be smaller than dimension T. In the multilayer ceramic capacitor 10, the dimensions T, W, and L of the ceramic element 11 can be arbitrarily determined within the range that satisfies the above conditions.
[0020] The first and second external electrodes 14 and 15 each have first and second end face covering portions 14a and 15a, and first and second extension portions 14b and 15b. The end face covering portions 14a and 15a cover the end faces E1 and E2 of the ceramic body 11. The extension portions 14b and 15b extend from the end face covering portions 14a and 15a to the main faces M1 and M2 and the side faces S1 and S2.
[0021] The extensions 14b and 15b cover a portion of the end faces E1 and E2 on the main surfaces M1 and M2 and the side surfaces S1 and S2, respectively, meaning they are spaced apart from each other on the main surfaces M1 and M2 and the side surfaces S1 and S2. As a result, the external electrodes 14 and 15 have U-shaped cross-sections parallel to the XZ plane and cross-sections parallel to the XY plane.
[0022] The ceramic body 11 is made of dielectric ceramics and has an electrode stacking portion 16 and a pair of cover portions 17. The pair of cover portions 17 cover the electrode stacking portion 16 from both sides in the Z-axis direction. In other words, in the ceramic body 11, the pair of cover portions 17 constitute the main surfaces M1 and M2, and the electrode stacking portion 16 and the pair of cover portions 17 constitute the end surfaces E1 and E2 and the side surfaces S1 and S2.
[0023] The ceramic body 11 has a structure in which multiple flat ceramic layers 18 extending along the XY plane are stacked in the Z-axis direction. The electrode stacking section 16 is arranged between the multiple ceramic layers 18 and has multiple sheet-like first and second internal electrodes 12 and 13 extending along the XY plane. The cover section 17 does not have internal electrodes 12 and 13.
[0024] The internal electrodes 12 and 13 are arranged alternately along the Z-axis direction and face each other in the Z-axis direction in the central opposing regions in the X-axis and Y-axis directions. The first internal electrode 12 is drawn out from the opposing region to the first end face E1 and connected to the first external electrode 14. The second internal electrode 13 is drawn out from the opposing region to the second end face E2 and connected to the second external electrode 15.
[0025] With this configuration, when a voltage is applied between the external electrodes 14 and 15 in the multilayer ceramic capacitor 10, a voltage is applied to multiple ceramic layers 18 between the internal electrodes 12 and 13 in the opposing region. As a result, the multilayer ceramic capacitor 10 stores a charge corresponding to the voltage between the external electrodes 14 and 15.
[0026] In the tall ceramic body 11, it is possible to increase the capacity by increasing the Z-axis dimension of the electrode stacking section 16 and thereby increasing the number of stacked internal electrodes 12 and 13. From this viewpoint, it is preferable that the total number of stacked layers, which is the sum of the number of stacked internal electrodes 12 and 13, be 500 or more in the ceramic body 11, and more preferably 700 or more.
[0027] In the ceramic substrate 11, a high dielectric constant dielectric ceramic is used to increase the capacitance of each ceramic layer 18 between the internal electrodes 12 and 13. Examples of high dielectric constant dielectric ceramics include perovskite materials containing barium (Ba) and titanium (Ti), such as barium titanate (BaTiO3).
[0028] Furthermore, dielectric ceramics may also be composed of elements such as strontium titanate (SrTiO3), calcium titanate (CaTiO3), magnesium titanate (MgTiO3), calcium zirconate (CaZrO3), calcium zirconate titanate (Ca(Zr,Ti)O3), barium calcium zirconate titanate ((Ba,Ca)(Zr,Ti)O3), barium zirconate (BaZrO3), and titanium dioxide (TiO2).
[0029] In the multilayer ceramic capacitor 10, the first and second external electrodes 14 and 15 are both formed primarily of copper (Cu), and the first and second internal electrodes 12 and 13 are both formed primarily of nickel (Ni). In this embodiment, the "main component" refers to the component with the highest content ratio.
[0030] In other words, in the multilayer ceramic capacitor 10, external electrodes 14 and 15 formed mainly of Cu and internal electrodes 12 and 13 formed mainly of Ni are connected at the end faces E1 and E2 of the ceramic body 11. The external electrodes 14 and 15 are formed as baked films that are baked onto the ceramic body 11.
[0031] When the external electrodes 14 and 15 are fired onto the ceramic body 11, the Cu in the external electrodes 14 and 15 reacts with the Ni that constitutes the internal electrodes 12 and 13 and diffuses into the internal electrodes 12 and 13. In other words, the Ni that constitutes the X-axis ends drawn out at the end faces E1 and E2 of the internal electrodes 12 and 13 reacts with the Cu to form a copper-nickel alloy.
[0032] As a result, the ends of the internal electrodes 12 and 13 that are drawn out to the end faces E1 and E2 expand due to the diffusion of Cu. Consequently, in the ceramic body 11, internal stress is generated as the ends of the internal electrodes 12 and 13 that expand in the X-axis direction attempt to expand in the Z-axis direction.
[0033] In the ceramic body 11, internal stresses tend to concentrate at the corners C due to the tendency of both ends in the X-axis direction to expand in the Z-axis direction. Here, the corners C in the ceramic body 11 refer to the eight parts that connect the three surfaces M1, M2, end faces E1, E2, and side faces S1, S2, as shown in Figure 1.
[0034] In particular, in the tall ceramic body 11, the greater the number of layers of internal electrodes 12 and 13, the greater the force that tends to expand in the Z-axis direction caused by the expansion of each internal electrode 12 and 13, resulting in a larger internal stress concentrated at the corner C. In the ceramic body 11, the greater the internal stress concentrated at the corner C, the more likely cracks are to occur at the corner C.
[0035] In a multilayer ceramic capacitor 10, if a crack occurs at the corner C of the ceramic body 11, the crack can become a pathway for moisture to enter, leading to a decrease in moisture resistance. Furthermore, since the corner C of the ceramic body 11 is covered by the external electrodes 14 and 15, it is difficult to detect cracks at the corner C through visual inspection.
[0036] Figure 4 is a cross-sectional view of the multilayer ceramic capacitor 10 along the line A2-A2' in Figure 1. Figure 5 is a cross-sectional view of the multilayer ceramic capacitor 10 along the line B2-B2' in Figure 1. Figures 4 and 5 show longitudinal cross-sections of the region of the multilayer ceramic capacitor 10 that includes the vicinity of the corner C of the ceramic element 11.
[0037] In the multilayer ceramic capacitor 10, non-existent regions F are provided near the eight corners C of the ceramic body 11, which are the ends of the X, Y, and Z axes in the electrode stacking portion 16, where the internal electrodes 12 and 13 are absent. In other words, by providing non-existent regions F in the ceramic body 11, the internal electrodes 12 and 13 are moved away from the corners C.
[0038] As a result, the ceramic body 11 is less affected by the internal electrodes 12 and 13 at the corners C. In addition, the non-existent region F in the ceramic body 11 acts to alleviate the internal stress caused by the expansion of the internal electrodes 12 and 13. As a result, cracks are less likely to occur at the corners C in the ceramic body 11.
[0039] The electrode stacking section 16 is composed of an inner layer section 16a and a pair of outer layer sections 16b, which are regions divided in the Z-axis direction. In the electrode stacking section 16, the pair of outer layer sections 16b are adjacent to a pair of cover sections 17, and the inner layer section 16a is located between the pair of outer layer sections 16b. In the electrode stacking section 16, non-existent regions F are provided in each of the pair of outer layer sections 16b.
[0040] The first and second internal electrodes 12 and 13 are composed of first and second inner layer internal electrodes 12a and 13a, and first and second outer layer internal electrodes 12b and 13b. In other words, the first internal electrode 12 is composed of the first inner layer internal electrode 12a and the first outer layer internal electrode 12b, and the second internal electrode 13 is composed of the second inner layer internal electrode 13a and the second outer layer internal electrode 13b.
[0041] In the electrode stacking section 16, the first and second inner layer internal electrodes 12a and 13a are stacked on the inner layer section 16a, and the first and second outer layer internal electrodes 12b and 13b are stacked on a pair of outer layer sections 16b, respectively. In other words, in the electrode stacking section 16, a region F is formed by the first and second outer layer internal electrodes 12b and 13b stacked on the pair of outer layer sections 16b.
[0042] Figures 6A and 6B are plan views showing one ceramic layer 18 in the inner layer portion 16a, where the inner layer internal electrodes 12a and 13a are formed, respectively. Specifically, Figure 6A shows the ceramic layer 18 on which the first inner layer internal electrode 12a is formed, and Figure 6B shows the ceramic layer 18 on which the second inner layer internal electrode 13a is formed.
[0043] As shown in Figures 6A and 6B, the inner layer internal electrodes 12a and 13a have a common planar shape. In other words, the first inner layer internal electrode 12a shown in Figure 6A and the second inner layer internal electrode 13a shown in Figure 6B are in a positional relationship where they are reversed left to right with respect to the central axis parallel to the Y axis passing through the center of the ceramic layer 18 in the X-axis direction.
[0044] Both the inner layer internal electrodes 12a and 13a have a rectangular planar shape defined by four corners D and are provided at a distance from the sides S1 and S2. Furthermore, the first inner layer internal electrode 12a is provided at a distance from the second end face E2, and the second inner layer internal electrode 13a is provided at a distance from the first end face E1.
[0045] Figures 7A and 7B are plan views showing one ceramic layer 18 in the outer layer portion 16b, where the outer layer internal electrodes 12b and 13b are formed, respectively. Specifically, Figure 7A shows the ceramic layer 18 on which the first outer layer internal electrode 12b is formed, and Figure 7B shows the ceramic layer 18 on which the second outer layer internal electrode 13b is formed.
[0046] As shown in Figures 7A and 7B, the outer layer internal electrodes 12b and 13b have a common planar shape. In other words, the first outer layer internal electrode 12b shown in Figure 7A and the second outer layer internal electrode 13b shown in Figure 7B are in a positional relationship where they are reversed left to right with respect to the central axis parallel to the Y axis passing through the center of the ceramic layer 18 in the X-axis direction.
[0047] Figures 7A and 7B show the outlines of the inner layer internal electrodes 12a and 13a with dashed lines. The outer layer internal electrodes 12b and 13b, which are laminated on the outer layer portion 16b, are positioned so as to avoid the vicinity of the corners C of the ceramic body 11 by ensuring that there are no portions corresponding to the four corners D of the inner layer internal electrodes 12a and 13a.
[0048] In other words, in the outer layer internal electrodes 12b and 13b, the regions including the parts corresponding to the four corners D of the inner layer internal electrodes 12a and 13a are defined as the first and second non-existent regions F1 and F2. In the ceramic body 11, the first and second non-existent regions F1 and F2 provided in the outer layer internal electrodes 12b and 13b constitute the non-existent region F of the pair of outer layer portions 16b.
[0049] In both the outer layer internal electrodes 12b and 13b, the width in the Y-axis direction is equivalent to that of the first inner layer internal electrode 12a at the center in the X-axis direction. Furthermore, in both the outer layer internal electrodes 12b and 13b, non-existent regions F1 and F2 are provided on both sides of the center in the X-axis direction, including portions corresponding to the four corners D of the inner layer internal electrodes 12a and 13a.
[0050] In the portion of the first outer layer internal electrode 12b on the first end face E1 side, first non-existent regions F1 are provided at both ends in the Y-axis direction, and only the central portion in the Y-axis direction is extended to the first end face E1 and connected to the first external electrode 14. As a result, the first outer layer internal electrode 12b has a planar shape that is narrowed in the Y-axis direction on the first end face E1 side.
[0051] In the portion of the second outer layer internal electrode 13b on the second end face E2 side, second non-existent regions F2 are provided at both ends in the Y-axis direction, and only the central portion in the Y-axis direction is extended to the second end face E2 and connected to the second external electrode 15. As a result, the second outer layer internal electrode 13b has a planar shape that is narrowed in the Y-axis direction on the second end face E2 side.
[0052] Furthermore, in the first outer layer internal electrode 12b, the entire portion on the second end face E2 side is designated as the first non-existent region F1. In the second outer layer internal electrode 13b, the entire portion on the first end face E1 side is designated as the second non-existent region F2. As a result, both the outer layer internal electrodes 12b and 13b have smaller dimensions in the X-axis direction than the inner layer internal electrodes 12a and 13a.
[0053] As shown in Figure 4, the outer layer portion 16b of the electrode stacking portion 16 has a non-existent region F in the entire X-axis direction opposite to the extended portions 14b and 15b of the external electrodes 14 and 15 in the Z-axis direction. In other words, in the outer layer internal electrodes 12b and 13b, the non-existent regions F1 and F2 extend beyond the extended portions 14b and 15b in the X-axis direction.
[0054] In other words, the first outer layer internal electrode 12b narrows in the Y-axis direction in the entire region facing the first extension 14b in the Z-axis direction, and does not face the second extension 15b in the Z-axis direction near the corner C. Similarly, the second outer layer internal electrode 13b narrows in the Y-axis direction in the entire region facing the second extension 15b in the Z-axis direction, and does not face the first extension 14b in the Z-axis direction near the corner C.
[0055] With this configuration, the multilayer ceramic capacitor 10 can suppress the occurrence of cracks throughout the entire portion of the ceramic body 11 covered by the external electrodes 14 and 15. As a result, the multilayer ceramic capacitor 10 can suppress the occurrence of defects that are difficult to identify by visual inspection.
[0056] Furthermore, it is preferable that the dimension in the Y-axis direction of the first outer layer internal electrode 12b in the region facing the first extension portion 14b in the Z-axis direction is two-thirds or less of that of the first inner layer internal electrode 12a. This makes it possible to more effectively suppress the occurrence of cracks in the portion of the ceramic body 11 covered by the first outer electrode 14.
[0057] Furthermore, it is preferable that the dimension in the Y-axis direction of the second outer layer internal electrode 13b in the region facing the second extension portion 15b in the Z-axis direction is two-thirds or less of that of the second inner layer internal electrode 13a. This makes it possible to more effectively suppress the occurrence of cracks in the portion of the ceramic body 11 covered by the second outer electrode 15.
[0058] In the ceramic body 11, the larger the Z-axis dimension of each outer layer 16b in the electrode stacked portion 16, the easier it is to suppress crack generation, but the more difficult it becomes to obtain a large capacity. From this viewpoint, it is preferable to set the Z-axis dimension of each outer layer 16b to 5% or more and 25% or less of the Z-axis dimension T of the ceramic body 11.
[0059] [Manufacturing method for multilayer ceramic capacitor 10] Figure 8 is a flowchart showing the manufacturing method of the multilayer ceramic capacitor 10 according to this embodiment. Figures 9 to 13 show the manufacturing process of the multilayer ceramic capacitor 10. Hereinafter, the manufacturing method of the multilayer ceramic capacitor 10 will be explained in reference to Figure 8, with appropriate reference to Figures 9 to 13.
[0060] (Step S01: Prepare the ceramic sheet) In step S01, first and second inner layer ceramic sheets 101a and 102a for forming the inner layer 16a of the electrode stacked portion 16, first and second outer layer ceramic sheets 101b and 102b for forming a pair of outer layer portions 16b of the electrode stacked portion 16, and a cover ceramic sheet 103 for forming the cover portion 17 are prepared.
[0061] Ceramic sheets 101a, 101b, 102a, 102b, and 103 are all composed of unfired dielectric green sheets with dielectric ceramics as the main component. Ceramic sheets 101a, 101b, 102a, 102b, and 103 are formed into sheets using, for example, a roll coater or a doctor blade.
[0062] Figure 9A is a plan view of the first inner layer ceramic sheet 101a. Figure 9B is a plan view of the second inner layer ceramic sheet 102a. Figure 10A is a plan view of the first outer layer ceramic sheet 101b. Figure 10B is a plan view of the second outer layer ceramic sheet 102b. Figure 11 is a plan view of the cover ceramic sheet 103.
[0063] At this stage, each ceramic sheet 101a, 102a, 101b, 102b, and 103 is composed of a large sheet that has not been separated into individual pieces. In Figures 9 to 11, the first cutting line Lx parallel to the X-axis and the second cutting line Ly parallel to the Y-axis are shown as dashed lines, representing the cutting lines when separating each multilayer ceramic capacitor 10 into individual pieces.
[0064] Unfired conductor patterns 112a and 113a corresponding to the inner layer internal electrodes 12a and 13a are formed on the inner layer ceramic sheets 101a and 102a. Unfired conductor patterns 112b and 113b corresponding to the outer layer internal electrodes 12b and 13b are formed on the outer layer ceramic sheets 101b and 102b.
[0065] Furthermore, the cover ceramic sheet 103 corresponding to the cover portion 17, which does not have internal electrodes, does not have an unfired conductive pattern formed on it. Also, the composition of the cover ceramic sheet 103 corresponding to the cover portion 17, which does not contribute to the formation of capacitance, may differ from that of the ceramic sheets 101a, 102a, 101b, and 102b.
[0066] The conductive patterns 112a, 113a, 112b, and 113b are formed by applying a conductive paste, mainly composed of Ni, to the ceramic sheets 101a, 102a, 101b, and 102b. The method for applying the conductive paste can be arbitrarily selected from known techniques; for example, screen printing or gravure printing can be used.
[0067] In conductor patterns 112a, 112b and conductor patterns 113a, 113b, gaps in the X-axis direction along the cutting line Ly are formed every other cutting line Ly. In conductor patterns 112a, 112b and conductor patterns 113a, 113b, the gaps are arranged alternately along the X-axis.
[0068] (Step S02: Lamination) In step S02, a laminated sheet 104 is fabricated by stacking the ceramic sheets 101a, 102a, 101b, 102b, and 103 prepared in step S01, as shown in Figure 12. For the sake of clarity, in Figure 12, the ceramic sheets 101a, 102a, 101b, 102b, and 103 are shown spaced apart from each other.
[0069] In the laminated sheet 104, inner layer ceramic sheets 101a and 102a are alternately stacked in the Z-axis direction at positions corresponding to the inner layer 16a of the electrode laminated section 16. In addition, outer layer ceramic sheets 101b and 102b are alternately stacked in the Z-axis direction at positions corresponding to the outer layer 16b of the electrode laminated section 16.
[0070] Furthermore, in the laminated sheet 104, cover ceramic sheets 103 corresponding to the cover portion 17 are laminated from both the upper and lower sides in the Z-axis direction of the ceramic sheets 101a, 102a, 101b, and 102b that are laminated at positions corresponding to the electrode laminated portion 16. The cover ceramic sheets 103 are laminated continuously in a number corresponding to the thickness of the cover portion 17.
[0071] (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 Figure 13 to obtain an unfired ceramic body 11. For cutting the laminated sheet 104 in step S03, for example, a cutting device equipped with a push-cutting blade or a dicing device equipped with a rotary blade can be used.
[0072] (Step S04: Firing) In step S04, the ceramic body 11 obtained in step S03 is fired. The firing temperature in step S04 can be approximately 1000 to 1300°C, for example, when using a barium titanate (BaTiO3)-based material. The firing can also be carried out, for example, under a reducing atmosphere or a low oxygen partial pressure atmosphere.
[0073] (Step S05: External electrode formation) In step S05, 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 body 11 obtained in step S04 in the X-axis direction. The external electrodes 14 and 15 are formed by applying a conductive paste mainly composed of Cu to the ceramic body 11 and firing it.
[0074] In step S05, Cu in the conductive paste reacts with Ni, which constitutes the internal electrodes 12 and 13, and diffuses into the internal electrodes 12 and 13. However, as described above, in the ceramic body 11, even if expansion occurs in the internal electrodes 12 and 13 due to the diffusion of Cu, the occurrence of cracks is suppressed by the action of the non-existent region F provided in the outer layer 16b.
[0075] [Other configuration examples of the outer layer 16b] In the ceramic body 11, it is sufficient that a region F is provided near the corner C of the outer layer 16b where the outer layer internal electrodes 12b and 13b are absent, and the configuration of the outer layer internal electrodes 12b and 13b is not limited to the above. In the following description, the term "absence region F" is also used as a general term for the first and second absence regions F1 and F2.
[0076] For example, in the outer layer internal electrodes 12b and 13b, as shown in Figure 14, the X-axis end opposite to the side drawn out to the end faces E1 and E2 may also have a non-existent region F at both ends in the Y-axis direction. In other words, the outer layer internal electrodes 12b and 13b may have a planar shape that is narrowed in the Y-axis direction on both sides in the X-axis direction.
[0077] Furthermore, in the outer layer internal electrodes 12b and 13b, as shown in Figure 15, a non-existent region F may be provided over the entire X-axis direction at both ends in the Y-axis direction. This makes it possible to suppress the occurrence of cracks in the ceramic body 11 over the entire ridge portion extending in the X-axis direction that connects the main surfaces M1 and M2 with the side surfaces S1 and S2.
[0078] Furthermore, in the ceramic body 11, it is preferable that a non-existent region F is provided near all eight corners C as described above, but if a non-existent region F is provided near at least one of the eight corners C, the effect of suppressing the occurrence of cracks in the corner C where the non-existent region F is provided nearby can be obtained.
[0079] In other words, for the outer layer internal electrodes 12b and 13b, it is sufficient that a non-existent region F is provided at a position corresponding to at least one of the four corners D of the inner layer internal electrodes 12a and 13a. For example, for the outer layer internal electrodes 12b and 13b, as shown in Figure 16, it is not necessary to provide a non-existent region F on one of the Y-axis directions of the X-axis direction ends that are drawn out to the end faces E1 and E2.
[0080] [Examples] As Examples 1 to 4 of the present invention, 100 samples of the multilayer ceramic capacitor 10 according to the above embodiment were each manufactured. In the samples according to Examples 1 to 4, the configurations of the outer layer internal electrodes 12b and 13b differ from each other, while the configurations other than the outer layer internal electrodes 12b and 13b are common to all.
[0081] In all of Examples 1 to 4, the dimensions L of the ceramic body 11 were set to 0.62 mm, W to 0.33 mm, and T to 0.55 mm, meaning that the dimension T of the ceramic body 11 was 1.7 times the dimension W. In addition, in all of Examples 1 to 4, the thickness of the electrode stacked portion 16 was set to 500 μm, the thickness of each cover portion 17 was set to 25 μm, and the dimensions of the extension portions 14b and 15b of the external electrodes 14 and 15 in the X-axis direction were set to 0.15 mm, respectively.
[0082] Furthermore, in all of Examples 1 to 4, the thickness of the internal electrodes 12 and 13, and the thickness of the ceramic layer 18 were set to approximately 0.5 μm. In addition, in all of Examples 1 to 4, the inner layer internal electrodes 12a and 13a were made to have a common rectangular planar shape, and the dimension of the inner layer internal electrodes 12a and 13a in the Y-axis direction was set to 0.3 μm.
[0083] Furthermore, in all of Examples 1 to 4, the total number of layers of internal electrodes 12 and 13 was set to 500. More specifically, in all of Examples 1 to 4, the total number of layers of internal electrodes 12a and 13a in the inner layer portion 16a was set to 400, and the total number of layers of external internal electrodes 12b and 13b in the pair of outer layer portions 16b was set to 50 each.
[0084] In Example 1, the outer layer internal electrodes 12b and 13b were configured as shown in Figure 7. In Example 2, the outer layer internal electrodes 12b and 13b were configured as shown in Figure 14. In Example 3, the outer layer internal electrodes 12b and 13b were configured as shown in Figure 15. In Example 4, the outer layer internal electrodes 12b and 13b were configured as shown in Figure 16.
[0085] In Examples 1, 2, and 4, the Y-axis dimension of the central part of the outer layer internal electrodes 12b and 13b in the X-axis direction was set to 0.3 μm. Furthermore, for the outer layer internal electrodes 12b and 13b, the Y-axis dimension of the ends in the X-axis direction drawn out to the end faces E1 and E2 in Examples 1 and 4, both ends in the X-axis direction in Example 2, and the entire length in Example 3 was set to 0.2 mm.
[0086] Furthermore, as Comparative Examples 1 and 2, 100 samples each were prepared with configurations different from the multilayer ceramic capacitor 10 according to the above embodiment. In the samples of Comparative Examples 1 and 2, all internal electrodes 12 and 13 had the same configuration as the inner layer internal electrodes 12a and 13a of the samples of Examples 1 to 4, meaning that the outer layer internal electrodes 12b and 13b were not provided.
[0087] In Comparative Example 1, the configuration was the same as in Examples 1 to 4, except for the above configuration. On the other hand, in Comparative Example 2, in addition to the above configuration, the ceramic body 11 was not tall, which differed from Examples 1 to 4. Specifically, the dimension T of the ceramic body 11 was set to 0.32 mm, meaning that the dimension T of the ceramic body 11 was 1.0 times the dimension W.
[0088] Accordingly, in Comparative Example 2, the thickness of the electrode stacked portion 16 was set to 270 μm, and the thickness of each cover portion 17 was set to 25 μm. In addition, in Comparative Example 2, the total number of stacked layers of the internal electrodes 12 and 13 was set to 270 layers. The sample for Comparative Example 2 had the same configuration as Examples 1 to 4 and Comparative Example 1, except for the configuration mentioned above.
[0089] Cross-sectional observation was performed on the samples related to Examples 1-4 and Comparative Examples 1 and 2 to confirm whether or not cracks occurred at the corners C of the ceramic body 11. In Examples 1-4, no cracks were observed at the corners C of the ceramic body 11 in any of the samples, confirming that the effects of the present invention were obtained.
[0090] In Comparative Example 1, crack formation was observed at one of the corners C of the ceramic body 11 in all samples, while in Comparative Example 2, no crack formation was observed at the corners C of the ceramic body 11 in any samples. This confirmed that crack formation at the corners C of the ceramic body 11 is a problem specific to the tall-profile type.
[0091] [Other embodiments] Although embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the embodiments described above and can be modified in various ways.
[0092] For example, in the ceramic body 11, the non-existent region F does not need to be provided in the entire region of the pair of outer layer portions 16b of the electrode stacked portion 16 that is facing the extended portions 14b and 15b of the external electrodes 14 and 15 in the Z-axis direction. The effects of the present invention can be obtained if the non-existent region F is provided in at least a portion of the region that is facing the extended portions 14b and 15b in the Z-axis direction.
[0093] Furthermore, in the multilayer ceramic capacitor 10 according to the present invention, the above effect can be obtained in a configuration in which the extensions 14b and 15b of the external electrodes 14 and 15 are provided on at least the main surfaces M1 and M2. For this reason, in the present invention, the extensions 14b and 15b of the external electrodes 14 and 15 do not need to be provided on the side surfaces S1 and S2. [Explanation of Symbols]
[0094] 10…Multilayer ceramic capacitor 11…Ceramic base 12,13…Internal electrode 12a, 13a... Inner layer internal electrodes 12b,13b...Outer layer internal electrode 14,15...External electrode 14a, 15a...End face covering part 14b,15b...extension part 16… Electrode stacking section 16a...Inner layer 16b...Outer layer part 17...Cover part 18…Ceramic layer M1,M2…main surface E1,E2…end face S1,S2…side C…Corner D...corner F,F1,F2…Non-existent area
Claims
1. A ceramic body comprising: an electrode stacking portion having multiple first and second internal electrodes mainly composed of Ni, which are alternately stacked along a first axis and drawn out to first and second end faces perpendicular to a second axis perpendicular to the first axis, respectively; and a pair of cover portions covering the electrode stacking portion from both sides in the first axis direction and forming first and second main surfaces perpendicular to the first axis, wherein the dimension in the first axis direction is 1.5 times or more the dimension in the third axis direction perpendicular to the first and second axes, The first and second external electrodes, which are mainly composed of Cu, have first and second end face covering portions that cover the first and second end faces, and first and second extension portions that extend from the first and second end face covering portions to the first and second main faces. It is equipped with, The plurality of first and second internal electrodes are composed of a plurality of first and second inner layer internal electrodes having a common rectangular planar shape, and a plurality of first and second outer layer internal electrodes, each having first and second non-existent regions provided at positions corresponding to at least the corners on the first and second end faces among the four corners of the plurality of first and second inner layer internal electrodes. In the second axial direction, the dimension in the third axial direction of the region on the first end face side of the first outer layer internal electrode is smaller than the dimension in the third axial direction of the central region of the first outer layer internal electrode by the dimension of the first absent region at the corner on the first end face side. In the second axial direction, the dimension of the region on the second end face side of the second outer layer internal electrode in the third axial direction is smaller than the dimension of the central region of the second outer layer internal electrode in the third axial direction by the dimension of the second absent region at the corner on the second end face side. The electrode stacking portion comprises a pair of outer layer portions adjacent to the pair of cover portions, on which the plurality of first and second outer layer internal electrodes are stacked, and an inner layer portion located between the pair of outer layer portions, on which the plurality of first and second inner layer internal electrodes are stacked. Multilayer ceramic capacitor.
2. A multilayer ceramic capacitor according to claim 1, The plurality of first and second outer layer internal electrodes are provided with the first and second non-existent regions at all positions corresponding to the four corners of the first and second inner layer internal electrodes. Multilayer ceramic capacitor.
3. A multilayer ceramic capacitor according to claim 1 or 2, The plurality of first outer layer internal electrodes have a planar shape that is narrowed in the third axial direction in the entire region facing the first extension in the first axial direction, The plurality of second outer layer internal electrodes have a planar shape that is narrowed in the third axial direction in the entire region facing the second extension in the first axial direction. Multilayer ceramic capacitor.
4. A multilayer ceramic capacitor according to claim 3, In the plurality of first outer layer internal electrodes, the dimension in the third axial direction in the region facing the first extension in the first axial direction is two-thirds or less of that of the plurality of first inner layer internal electrodes. In the plurality of second outer layer internal electrodes, the dimension in the third axial direction in the region facing the second extension in the first axial direction is two-thirds or less of that of the plurality of second inner layer internal electrodes. Multilayer ceramic capacitor.
5. A multilayer ceramic capacitor according to claim 1 or 2, The plurality of first outer layer internal electrodes do not face the second extension in the first axial direction. The plurality of second outer layer internal electrodes are not facing the first extension in the first axial direction. Multilayer ceramic capacitor.