Multilayer ceramic electronic components

Abstract

To provide a multilayer ceramic electronic component that can increase reliability, and a method for manufacturing the same.SOLUTION: A multilayer ceramic electronic component is provided with: a functional part that has internal electrodes stacked in a first direction; a cover part that covers the functional part from the first direction; and a side margin part that covers the functional part from a second direction orthogonal to the first direction. The functional part has, on a predetermined cross section, first straight line parts in contact with the cover part and extending in the second direction, second straight line parts in contact with the side margin part and extending in the first direction, and corner parts connecting the first straight line parts and the second straight line parts. When the distance along the first direction between a first virtual line obtained by extending the first straight line part in the second direction and an end point of the second straight line part on a side of the first virtual line is defined as a, and the distance along the second direction between a second virtual line obtained by extending the second straight line part in the first direction and an end point of the first straight line part on a side of the second virtual line is defined as b, the corner part is curved so as to satisfy the conditions of a≥1 μm and 0.1≤a / b≤0.4.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a multilayer ceramic electronic component such as a multilayer ceramic capacitor and a method for manufacturing the same. [Background technology]

[0002] In recent years, as electronic devices have become smaller and their performance has improved, there has been an increasing demand for smaller and larger capacitance multilayer ceramic capacitors used in electronic devices. Enlarging the internal electrodes of multilayer ceramic capacitors is an effective way to meet this demand. To enlarge the internal electrodes, it is necessary to thin the side margins that ensure insulation around the internal electrodes.

[0003] Patent Document 1 discloses a technique for retrofitting side margins in order to reduce the thickness of the side margins. In this technique, a ceramic protective layer (side margin) is provided on the side surface of a green chip with the internal electrodes exposed on the side surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-209539 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the technology described in Patent Document 1, when the side margin portion becomes thin, sufficient moisture resistance cannot be obtained, making it difficult to improve reliability.

[0006] In view of the above circumstances, an object of the present invention is to provide a multilayer ceramic electronic component that can improve reliability, and a method for manufacturing the same. [Means for solving the problem]

[0007] To achieve the above object, a multilayer ceramic electronic component according to one embodiment of the present invention includes a functional portion, a cover portion, and a side margin portion. The functional section has internal electrodes stacked in a first direction. The cover portion covers the functional portion from the first direction. The side margin portion covers the functional portion from a second direction perpendicular to the first direction. The functional portion divides the functional portion into two equal parts in a third direction perpendicular to the first direction and the second direction, and in a cross section perpendicular to the third direction, has a first straight portion that is in contact with the cover portion and extends in the second direction, a second straight portion that is in contact with the side margin portion and extends in the first direction, and a corner portion that connects the first straight portion and the second straight portion. The corner portion is When the distance along the first direction between a first virtual line along which the first straight line portion is extended in the second direction and the end point of the second straight line portion on the side of the first virtual line is a, and the distance along the second direction between a second virtual line along which the second straight line portion is extended in the first direction and the end point of the first straight line portion on the side of the second virtual line is b, the curve satisfies the conditions a≧1 μm and 0.1≦a / b≦0.4.

[0008] In this configuration, the functional portion has corners that are curved so that a≧1 μm and 0.1≦a / b≦0.4 are satisfied. By satisfying the conditions of a≧1 μm and a / b≧0.1 for the corners, a sufficient distance can be secured from the surface of the multilayer ceramic electronic component to the ends of the outermost internal electrodes, thereby suppressing deterioration in moisture resistance. Additionally, by satisfying the condition of a / b≦0.4 for the corners, the outermost internal electrodes can be prevented from curving sharply. This suppresses short circuits between internal electrodes adjacent in the first direction. Therefore, with the above configuration, it is possible to suppress deterioration in moisture resistance and short circuits, resulting in a highly reliable multilayer ceramic electronic component.

[0009] The thickness of the side margin portion may be 10 μm or more and 15 μm or less. Furthermore, the thickness of the side margin portion may be 12 μm or less. This ensures sufficient moisture resistance even when the side margins are very thin, thereby making it possible to obtain a multilayer ceramic electronic component that is small, has a large capacity, and is highly reliable.

[0010] The corner portion may be curved inward in the first direction from the end point of the first straight line portion on the second imaginary line side toward the end point of the second straight line portion on the first imaginary line side.

[0011] Specifically, the functional portion may have four corners in the cross section.

[0012] A method for manufacturing a multilayer ceramic electronic component according to another aspect of the present invention includes a step of producing a laminate sheet by stacking, in the first direction, a third ceramic sheet, on an outer surface in the first direction of a laminate in which first ceramic sheets and second ceramic sheets, each having a plurality of internal electrodes formed thereon, are alternately stacked in the first direction. The laminated sheet is pressure-bonded from the first direction. By cutting the laminated sheet, a laminated chip having a functional section having internal electrodes laminated in the first direction, a cover section covering the functional section from the first direction, and a side surface on which the internal electrodes are exposed and facing a second direction perpendicular to the first direction, The functional portion is formed by dividing the functional portion into two equal parts in a third direction perpendicular to the first direction and the second direction, and in a cross section perpendicular to the third direction, the functional portion is in contact with the cover portion and extends in the second direction. a first linear portion extending in the first direction, a second linear portion contacting the side margin portion and extending in the first direction, and a corner portion connecting the first linear portion and the second linear portion, The corner portion has a distance along the first direction between a first virtual line along which the first straight line portion is extended in the second direction and an end point of the second straight line portion on the side of the first virtual line as a, and a distance along the second direction between a second virtual line along which the second straight line portion is extended in the first direction and an end point of the first straight line portion on the side of the second virtual line as b, such that a≧1 μm and 0.1≦a / b Curved to satisfy the condition of ≦0.4, A stacked chip is fabricated. A side margin portion is formed on the side surface.

[0013] In addition, in the first ceramic sheet and the second ceramic sheet, the internal electrodes are arranged spaced apart from one another in the second direction with no-electrode-formed regions interposed therebetween. In the process of pressing from the first direction, a functional region in which the multiple internal electrodes are stacked in the first direction and a cutout region in which the non-electrode forming region is stacked and adjacent to the functional region in the second direction, and configured so that the thickness in the first direction gradually decreases as the region moves away from the functional region in the second direction, are formed in the laminated sheet. In the step of cutting the laminated sheet, the cutting region is cut out. In the region adjacent to the cut-out region of the functional region, the internal electrodes are curved inward in the first direction by crimping, thereby forming curved corners that satisfy the above-mentioned condition. [Effects of the Invention]

[0014] As described above, the present invention can provide a multilayer ceramic electronic component and a method for manufacturing the same that can improve reliability. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a perspective view of a multilayer ceramic capacitor according to an embodiment of the present invention; [Figure 2] FIG. 2 is a cross-sectional view taken along line AA' of the multilayer ceramic capacitor. [Figure 3]FIG. 2 is a cross-sectional view taken along line BB' of the multilayer ceramic capacitor. [Figure 4] 4 is a flowchart showing a method for manufacturing the multilayer ceramic capacitor. [Figure 5] 3A to 3C are plan views illustrating a manufacturing process of the multilayer ceramic capacitor. [Figure 6] 3A to 3C are perspective views illustrating a manufacturing process of the multilayer ceramic capacitor. [Figure 7] 3A to 3C are cross-sectional views showing a manufacturing process of the multilayer ceramic capacitor. [Figure 8] 3A to 3C are perspective views illustrating a manufacturing process of the multilayer ceramic capacitor. [Figure 9] 3A to 3C are perspective views illustrating a manufacturing process of the multilayer ceramic capacitor. [Figure 10] FIG. 4 is an enlarged cross-sectional view of a part of FIG. 3. [Figure 11] 1A is a diagram schematically showing a cross section of the multilayer ceramic capacitor taken along line B-B', and FIG. 1B is a diagram schematically showing a similar cross section of a multilayer ceramic capacitor according to a comparative example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, X-axis, Y-axis, and Z-axis, which are mutually orthogonal, are shown as appropriate, and are common to all the drawings.

[0017] [Configuration of multilayer ceramic capacitor 10] 1 to 3 are diagrams showing a multilayer ceramic capacitor 10 according to one embodiment of the present invention. Fig. 1 is a perspective view of the multilayer ceramic capacitor 10. Fig. 2 is a cross-sectional view of the multilayer ceramic capacitor 10 taken along line A-A' in Fig. 1. Fig. 3 is a cross-sectional view of the multilayer ceramic capacitor 10 taken along line B-B' in Fig. 1.

[0018] The multilayer ceramic capacitor 10 includes a ceramic body 11, a first external electrode 14, and a second external electrode 15. The ceramic body 11 typically has two main surfaces facing the Z-axis direction, two end faces facing the X-axis direction, and two side surfaces facing the Y-axis direction. For example, the ridges 11d connecting the respective faces of the ceramic body 11 are rounded.

[0019] The external electrodes 14, 15 cover the end faces of the ceramic body 11 and face each other in the X-axis direction with the ceramic body 11 in between. The external electrodes 14, 15 extend from the end faces of the ceramic body 11 to the main surfaces and side surfaces. As a result, the cross sections of the external electrodes 14, 15 parallel to the XZ plane and the XY plane are both U-shaped. Note that the shapes of the external electrodes 14, 15 are not limited to those shown in FIG. 1 .

[0020] The external electrodes 14, 15 are made of a good electrical conductor. Examples of good electrical conductors that form the external electrodes 14, 15 include metals or alloys containing copper (Cu), nickel (Ni), tin (Sn), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), or the like as a main component.

[0021] The ceramic body 11 has a laminate 16 and a side margin portion 17. The laminate 16 has two end faces 16a facing the X-axis direction, two side faces 16b facing the Y-axis direction, and two main faces 16c facing the Z-axis direction.

[0022] The side margin portions 17 cover the two side surfaces 16b of the laminate 16, respectively, and cover the capacitance forming portions 18 from the Y-axis direction. The thickness dimension of the side margin portions 17 in the Y-axis direction can be, for example, 15 μm or less, more preferably 12 μm or less. This allows the multilayer ceramic capacitor 10 to be miniaturized and have a high capacitance. The thickness dimension of the side margin portions 17 in the Y-axis direction can be, for example, 10 μm or more. This allows the multilayer ceramic capacitor 10 to have a high moisture resistance. The thickness dimension of the side margin portions 17 in the Y-axis direction is the largest dimension in the Y-axis direction from the side surface of the ceramic body 11 facing the Y-axis direction to the side surface 16b of the laminate 16.

[0023] The laminate 16 has a capacitance forming portion 18 and a cover portion 19 that covers the capacitance forming portion 18 from the Z-axis direction. The capacitance forming portion 18 has a first internal electrode 12 and a second internal electrode 13 that are laminated in the Z-axis direction with ceramic layers interposed between them. The capacitance forming portion 18 is configured as a functional portion in this embodiment.

[0024] The internal electrodes 12, 13 are each formed in a sheet shape extending along the XY plane. The first internal electrode 12 extends in the X-axis direction to one end face 16a and is connected to the first external electrode 14. The second internal electrode 13 extends in the X-axis direction to the other end face 16a and is connected to the second external electrode 15. As a result, when a voltage is applied between the first external electrode 14 and the second external electrode 15, the voltage is applied to the ceramic layer between the first internal electrode 12 and the second internal electrode 13, and a charge corresponding to the voltage is stored in the capacitance forming portion 18.

[0025] The internal electrodes 12 and 13 are made of a good electrical conductor. Typical examples of good electrical conductors that form the internal electrodes 12 and 13 include nickel (Ni), as well as metals or alloys containing copper (Cu), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), or the like as their main components.

[0026] The ceramic body 11 uses a dielectric ceramic with a high dielectric constant to increase the capacitance of each ceramic layer between the internal electrodes 12 and 13. Examples of dielectric ceramic with a high dielectric constant include materials with a perovskite structure containing barium (Ba) and titanium (Ti), such as barium titanate (BaTiO).

[0027] The ceramic layer may also be made of strontium titanate (SrTiO3), calcium titanate (CaTiO3), magnesium titanate (MgTiO3), calcium zirconate (CaZrO3), calcium titanate zirconate (Ca(Zr,Ti)O3), barium zirconate (BaZrO3), titanium oxide (TiO2), or the like.

[0028] The cover portion 19 and the side margin portion 17 are made of insulating ceramics, but may contain, for example, the dielectric ceramics used in the capacitance forming portion 18. This suppresses internal stress that may occur between the cover portion 19 and the side margin portion 17 and the capacitance forming portion 18.

[0029] The internal electrodes 12, 13 are formed across the entire width of the capacitance forming portion 18 in the Y-axis direction, and their peripheral edges 12b, 13b in the Y-axis direction are disposed on both side surfaces 16b of the laminate 16. In this embodiment, the peripheral edges 12b, 13b of the internal electrodes 12, 13 have a shape that curves inward in the Z-axis direction. The peripheral edges 12b, 13b of the internal electrodes 12, 13 tend to curve more inward in the Z-axis direction as they are disposed further outward in the Z-axis direction. Details of this curved shape This will be discussed later. The multilayer ceramic capacitor 10 having the curved peripheral edge portions 12b, 13b of the internal electrodes 12, 13 is manufactured, for example, by the following manufacturing method.

[0030] [Method of manufacturing the multilayer ceramic capacitor 10] Fig. 4 is a flowchart showing a method for manufacturing the multilayer ceramic capacitor 10. Figs. 5 to 9 are diagrams schematically showing the manufacturing process of the multilayer ceramic capacitor 10. The method for manufacturing the multilayer ceramic capacitor 10 will be described below along Fig. 4 with appropriate reference to Figs. 5 to 9.

[0031] (Step S01: Laminating ceramic sheets) In step S01, a first ceramic sheet 101 and a second ceramic sheet 102 for forming the capacitance forming portion 18, and a third ceramic sheet 103 for forming the cover portion 19 are prepared and then laminated.

[0032] The ceramic sheets 101, 102, and 103 are formed as unfired dielectric green sheets whose main component is dielectric ceramic. 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, 102, and 103 can be adjusted as appropriate.

[0033] FIG. 5 is a plan view of the ceramic sheets 101 and 102. At this stage, the ceramic sheets 101 and 102 are configured as large sheets that have not yet been singulated. FIG. 5 shows cutting lines Lx1, Lx2, Ly1, and Ly2 for singulating each multilayer ceramic capacitor 10. The cutting lines Lx1 and Lx2 are parallel to the X-axis, and the cutting lines Ly1 and Ly2 are parallel to the Y-axis. Note that the midpoint line Lc is an imaginary line extending between adjacent cutting lines Lx1 and Lx2 at a position that divides the space between them into two equal parts.

[0034] As shown in Fig. 5, an unfired first internal electrode 112 corresponding to the first internal electrode 12 is formed on the first ceramic sheet 101, and an unfired second internal electrode 113 corresponding to the second internal electrode 13 is formed on the second ceramic sheet 102. Although not shown in Fig. 5, no internal electrode is formed on the third ceramic sheet 103 corresponding to the cover portion 19.

[0035] The internal electrodes 112, 113 can be formed by applying any conductive paste to the ceramic sheets 101, 102. The method for applying the conductive paste can be selected from known techniques. For example, the conductive paste can be applied by screen printing or gravure printing.

[0036] In the first ceramic sheet 101, a first row in which the internal electrodes 112 extending across the cutting line Ly1 are arranged along the X-axis direction and a second row in which the internal electrodes 112 extending across the cutting line Ly2 are arranged along the X-axis direction are alternately arranged in the Y-axis direction. In the first row, the internal electrodes 112 adjacent to each other in the X-axis direction face each other across the cutting line Ly2. In the second row, the internal electrodes 112 adjacent to each other in the X-axis direction face each other across the cutting line Ly1. That is, in the first row and the second row adjacent to each other in the Y-axis direction, the internal electrodes 112 are arranged with a one-chip offset in the X-axis direction. The first internal electrodes 112 are arranged across the midline Lc in the Y-axis direction. The outer edges of each first internal electrode 112 in the Y-axis direction extend along the cutting lines Lx1 and Lx2.

[0037] The internal electrodes 113 on the second ceramic sheet 102 are configured in the same manner as the internal electrodes 112. However, on the second ceramic sheet 102, the internal electrodes 113 in the row corresponding to the first row on the first ceramic sheet 101 extend across the cutting line Ly2, and the internal electrodes 113 in the row corresponding to the second row on the first ceramic sheet 101 extend across the cutting line Ly1. In other words, the internal electrodes 113 are formed offset by one chip in the X-axis or Y-axis direction from the internal electrodes 112. The second internal electrodes 113 are arranged in the Y-axis direction, sandwiching the midline Lc therebetween. The outer edges of each second internal electrode 113 in the Y-axis direction extend along the cutting lines Lx1 and Lx2.

[0038] In the first ceramic sheet 101, electrode-free regions N1, where the internal electrodes 112 are not applied, are formed in a grid pattern along the intermediate line Lc and the cutting line Ly2. Similarly, in the second ceramic sheet 102, electrode-free regions N2, where the internal electrodes 113 are not applied, are formed in a grid pattern along the intermediate line Lc and the cutting line Ly1. In other words, the electrode-free regions N1 and N2 are configured to overlap on the intermediate line Lc between the cutting lines Lx1 and Lx2.

[0039] These ceramic sheets 101, 102, and 103 are stacked as shown in Fig. 6 to produce a laminated sheet 104. Specifically, the first ceramic sheets 101 and the second ceramic sheets 102 are alternately stacked, and a third ceramic sheet 103 is stacked on the top and bottom surfaces in the Z-axis direction of the stack of ceramic sheets 101 and 102. In the example shown in Fig. 6, four third ceramic sheets 103 are stacked on each side, but the number of third ceramic sheets 103 can be changed as appropriate.

[0040] (Step S02: Crimping) In step S02, the laminated sheet 104 is pressure-bonded in the Z-axis direction.

[0041] FIG. 7 is a schematic cross-sectional view of laminated sheet 104 as viewed from the X-axis direction, illustrating the pressure bonding step in step S02. In the pressure bonding process of this step, a pair of pressure plates S1 are placed opposite each other so as to sandwich the laminated sheet 104 in the Z-axis direction, and the pressure plates S1 are pressed against the laminated sheet 104 to compress the laminated sheet 104. The pressure plates S1 are pressed by, for example, hydrostatic pressure or uniaxial pressure.

[0042] Furthermore, an elastic sheet S2 is disposed between the pressure plate S1 and the laminate sheet 104. The elastic sheet S2 is made of a sheet-like elastic material, for example, polyethylene terephthalate (PET) resin. The elastic sheet S2 is pressed toward the laminate sheet 104 by the pressure plate S1.

[0043] The laminated sheet 104 is formed with a capacitance forming region (functional region) 105 where both the internal electrodes 112, 113 are laminated, and a cutout region 106 where both the electrode-free regions N1, N2 are laminated. The capacitance forming region 105 corresponds to the capacitance forming portion 18 and the cover portion 19 that covers the top and bottom of the capacitance forming portion 18. The cutout region 106 is an area adjacent to the capacitance forming region 105 in the Y-axis direction, where the internal electrodes 112, 113 are not laminated. In other words, the cutout region 106 is an area sandwiched between cutting lines Lx1, Lx2, and is cut out in a cutting process described below.

[0044] During compression bonding, the thickness of the cutout region 106 of the elastic sheet S2 in the Z-axis direction becomes greater than the thickness of the capacitance formation region 105 in the Z-axis direction. By applying pressure to the laminated sheet 104 with the elastic sheet S2 interposed therebetween, it is possible to form the cutout region 106 in a shape that is sunken inward in the Z-axis direction, as will be described below.

[0045] In the capacitance forming region 105, the ceramic sheets 101 and 102 on which the internal electrodes 112 and 113 are formed are stacked without any gaps. As a result, the capacitance forming region 105 is stretched entirely in the XY plane during the compression bonding process and compressed almost uniformly. As a result, a substantially flat surface is formed on the capacitance forming region 105.

[0046] On the other hand, gaps corresponding to the non-electrode forming regions N1 and N2 are formed in the cut-out region 106 before pressure is applied. The green sheet is softer and more stretchable than the internal electrodes 112 and 113. Therefore, when pressure is applied, the green sheet stretched from the capacitance forming region 105 enters the gaps.

[0047] Furthermore, the elastic sheet S2 is arranged thicker in the cutout region 106 than in the capacitance formation region 105, and can apply a sufficient load to the thinner cutout region 106 due to elastic deformation. As a result, in the cutout region 106, the green sheet extended from the capacitance formation region 105 and the green sheets stacked before pressure application are compressed in the Z-axis direction while extending in the XY plane. Therefore, in the cutout region 106, the thickness between the internal electrodes 12 and 13 gradually decreases from the cutting lines Lx1 and Lx2 on the capacitance formation region 105 side toward the midline Lc. In other words, the cutout region 106 is configured so that its thickness in the Z-axis direction gradually decreases as it moves away from the capacitance formation region 105 in the Y-axis direction. As a result, the cutout region 106 is formed so as to sink significantly inward in the Z-axis direction near the midline Lc.

[0048] As the cutout region 106 sinks, the peripheral portions 112b, 113b of the internal electrodes 112, 113 adjacent to the cutout region 106 also curve inward in the Z-axis direction. More specifically, the peripheral portions 112b, 113b are subjected to a force inward in the Z-axis direction by the elastic sheet S2 that bites into the cutout region 106, causing them to curve. The peripheral portions 112b, 113b may also be subjected to a force inward in the Z-axis direction by the laminate of ceramic sheets 103 that is stretched from the center side of the capacitance formation region 105. This results in the formation of curved peripheral portions 112b, 113b in the internal electrodes 112, 113. The internal electrodes 112, 113 located more outward in the Z-axis direction are more likely to be subjected to a force inward in the Z-axis direction, and therefore curve more inward in the Z-axis direction.

[0049] In Figures 8 and 9, the area outside the peripheral portions 112b and 113b on the main surface facing the Z-axis direction is depicted as being approximately flat, but this area may be curved inward in the Z-axis direction, similar to the peripheral portions 112b and 113b.

[0050] (Step S03: Cutting) In step S03, the laminated sheet 104 bonded in step S02 is cut along cutting lines Lx1, Lx2, Ly1, and Ly2 to produce unsintered laminated chips 116 shown in Fig. 8. The laminated chips 116 correspond to the laminated body 16 after firing. A press cutter blade or a rotary blade, for example, can be used to cut the laminated sheet 104 in this step.

[0051] When cutting along the cutting lines Lx1 and Lx2 with a push cutter blade, the blade can be brought into contact with each of the cutting lines Lx1 and Lx2 because the width of the blade is relatively narrow. This cuts the laminated sheet 104 along each of the cutting lines Lx1 and Lx2, and removes the resection region 106 between the cutting lines Lx1 and Lx2, thereby forming each laminated chip 116.

[0052] When cutting along the cutting lines Lx1 and Lx2 with a rotary blade, the blade is brought into contact with the entire resection region 106, including the cutting lines Lx1 and Lx2, because the width of the blade is relatively wide. As a result, the resection region 106 is cut by the rotary blade, and each stacked chip 116 is formed.

[0053] As shown in Fig. 8, the laminated chip 116 has side surfaces 116b formed as cut surfaces corresponding to the cutting lines Lx1 and Lx2. Peripheral edge portions 112b and 113b of the internal electrodes 112 and 113 are exposed from the side surfaces 116b. The peripheral edge portions 112b and 113b curve inward in the Z-axis direction as they approach the side surfaces 116b. Meanwhile, the laminated chip 116 has end surfaces 116a formed as cut surfaces corresponding to the cutting lines Ly1 and Ly2. One of the internal electrodes 112 and 113 is exposed from the end surfaces 116a.

[0054] More specifically, the laminated chip 116 has an unsintered capacitance forming portion 118 corresponding to the capacitance forming portion 18, and an unsintered cover portion 119 corresponding to the cover portion 19. In the capacitance forming portion 118, the internal electrodes 112, 113 are alternately laminated between green sheets corresponding to the ceramic layers. Because the peripheral portions 112b, 113b of the internal electrodes 112, 113 are curved, the capacitance forming portion 118 has a rectangular shape with rounded corners in cross section as viewed from the X-axis direction.

[0055] (Step S04: Forming side margins) In step S04, unsintered side margin portions 117 are formed on side surfaces 116b of the laminated chip 116 obtained in step S03, where the internal electrodes 112, 113 are exposed, thereby producing an unsintered ceramic body 111 as shown in FIG.

[0056] Side margin portion 117 includes an unfired ceramic material, and specifically is formed from a ceramic sheet or ceramic slurry. Side margin portion 117 can be formed, for example, by attaching a ceramic sheet to side surface 116b of laminated chip 116. Side margin portion 117 can also be formed by coating side surface 116b of laminated chip 116 with ceramic slurry by, for example, painting or dipping.

[0057] (Step S05: Firing) In step S05, the green ceramic body 111 obtained in step S04 is fired. The firing temperature in step S05 can be determined based on the sintering temperature of the ceramic body 111. Furthermore, firing can be performed, for example, in a reducing atmosphere or a low-oxygen partial pressure atmosphere.

[0058] (Step S06: Barrel polishing) In step S06, the fired ceramic body 111 is subjected to barrel polishing. Barrel polishing is performed, for example, by sealing a plurality of ceramic bodies 111 in a barrel container and rotating or vibrating the barrel container. The barrel container may contain a polishing medium or liquid together with the plurality of ceramic bodies 111. As a result, ridges 11d connecting the surfaces of the ceramic body 111 are chamfered, and the ceramic body 11 shown in FIGS. 1 to 3 is produced.

[0059] The barrel polishing in step S06 may be performed on ceramic body 111 before firing. That is, the barrel polishing in step S06 may be performed before the firing step in step S05.

[0060] (Step S07: Forming external electrodes) In step S07, external electrodes 14, 15 are formed on both ends in the X-axis direction of the ceramic body 11 obtained in step S06. The method for forming the external electrodes 14, 15 in step S07 can be selected from known methods. In this way, the multilayer ceramic capacitor 10 as shown in FIGS. 1 to 3 is formed.

[0061] Note that part of the processing in step S07 may be performed before step S05. For example, before step S05, unsintered electrode material may be applied to both end surfaces in the X-axis direction of the unsintered ceramic body 111, and in step S05, the unsintered electrode material may be fired simultaneously with firing the unsintered ceramic body 111 to form base layers for the external electrodes 14, 15. Alternatively, the unsintered electrode material may be applied to the ceramic body 111 that has been subjected to a binder removal process, and then these may be fired simultaneously.

[0062] This completes the multilayer ceramic capacitor 10. In this manufacturing method, the side margin portions 17 are added to the side surfaces 16b of the laminate 16 where the internal electrodes 12, 13 are exposed, so that the positions of the ends of the multiple internal electrodes 12, 13 in the ceramic body 11 in the Y-axis direction are aligned along the Z-axis direction with a variation of 0.5 μm or less.

[0063] Furthermore, curved peripheral portions 12b and 13b corresponding to the peripheral portions 112b and 113b are formed on the fired internal electrodes 12 and 13. These peripheral portions 12b and 13b give the capacitance forming portion 18 a cross-sectional shape as described below.

[0064] [Detailed configuration of capacitance forming portion 18] The capacitance generating portion 18 is configured in a rectangular shape with rounded corners in a cross section (cross section along line B-B') that divides the capacitance generating portion 18 in half in the X-axis direction and is perpendicular to the X-axis direction. The cross section along line B-B' will be referred to as the "B-B' cross section" hereinafter.

[0065] 3, in the cross section, the capacitance forming portion 18 has two first linear portions 181 that contact the cover portion 19 and extend in the Y-axis direction, two second linear portions 182 that contact the side margin portion 17 and extend in the Z-axis direction, and four corner portions 183 that connect the first linear portions 181 and the second linear portions 182. The two first linear portions 181 face each other in the Z-axis direction, and the two second linear portions 182 face each other in the Y-axis direction.

[0066] In the B-B' cross section, the capacitance forming portion 18 is configured to be substantially line-symmetrical with respect to the Y-axis direction and the Z-axis direction. Therefore, hereinafter, the configuration of one corner portion 183 and the first straight portion 181 and second straight portion 182 connected thereto will be described in detail with reference to Figure 10, which is an enlarged cross-sectional view of Figure 3.

[0067] 10, the first straight portion 181 is a straight portion extending in the Y-axis direction and is constituted by the internal electrodes 12, 13 in the outermost layer in the Z-axis direction. Note that the first straight portion 181 only needs to be substantially straight, and may meander or curve in the Z-axis direction within a small range, for example, within 1% of the height dimension of the ceramic body 11 in the Z-axis direction.

[0068] The outermost internal electrodes 12, 13 are referred to as outermost internal electrodes E. The outermost internal electrode E includes a flat portion E1 that forms the first linear portion 181, and a peripheral portion E2 that is located on the periphery of the flat portion E1 in the Y-axis direction and curves inward in the Z-axis direction from the flat portion E1. Note that the flat portion E1 only needs to be substantially flat, and may have slight irregularities in the Z-axis direction within a range of, for example, 1% or less of the height dimension of the ceramic body 11 in the Z-axis direction. An end point P1 of the first straight portion 181 is located at the boundary between the flat portion E1 and the peripheral edge portion E2.

[0069] The second linear portion 182 is a linear portion extending in the Z-axis direction and is formed by the side surface 16b of the laminate 16. The second linear portion 182 may be substantially linear, and may meander or curve in the Y-axis direction within a small range, for example, within 0.5% of the width dimension of the ceramic body 11 in the Y-axis direction. An end point P2 of the second straight portion 182 is formed by a tip end Ea2 of the peripheral edge E2 of the outermost internal electrode E in the Y-axis direction.

[0070] The corner portion 183 is a curved portion connecting the end point P1 of the first straight portion 181 and the end point P2 of the second straight portion 182. The corner portion 183 is formed by the peripheral edge portion E2 of the outermost layer internal electrode E. The corner portion 183 curves inward in the Z-axis direction from the end point P1 of the first straight portion 181 toward the end point P2 of the second straight portion 182.

[0071] The shape of corner 183 is defined by the following values ​​of a and a / b, where a is a value corresponding to the height dimension of corner 183 along the Z-axis direction, and b is a value corresponding to the length dimension of corner 183 along the Y-axis direction. This defines a preferred shape of corner 183.

[0072] More specifically, a is the distance along the Z-axis direction between a first imaginary line L1 extended from the first straight line portion 181 and an end point P2 of the second straight line portion 182 on the first imaginary line L1 side. The value of a can be controlled by the number of laminated ceramic sheets 101, 102 or the thickness of the ceramic sheets 101, 102. Alternatively, the value of a can be controlled by the elastic modulus of the elastic sheet S2, the load applied by the pressure plate S1, etc. in the pressure bonding process in step S02 described above.

[0073] The value b is the distance along the Y-axis direction between the second imaginary line L2 to which the second straight line portion 182 is extended and the end point P1 on the second imaginary line L2 side of the first straight line portion 181. The value of b can be controlled by the number of laminated ceramic sheets 101, 102 or the thickness of the ceramic sheets 101, 102, as well as the elastic modulus of the elastic sheet S2 and the load applied by the pressure plate S1 in the pressure bonding process in step S02 described above.

[0074] The corners 183 are curved so as to satisfy the conditions a≧1 μm and 0.1≦a / b≦0.4. Of the above conditions, when the corners 183 satisfy a≧1 μm and a / b≧0.1, the peripheral edge E2 of the outermost internal electrode E can be sufficiently curved, and the moisture resistance can be improved as described below.

[0075] 11(A) is a diagram schematically showing the B-B' cross section of the ceramic body 11 according to this embodiment, with the region occupied by the capacitance forming portion 18 surrounded by a dashed line. FIG. 11(B) is a diagram schematically showing the B-B' cross section of the ceramic body 21 according to a comparative example of this embodiment, with the region occupied by the capacitance forming portion 28 surrounded by a dashed line.

[0076] In the ceramic bodies 11 and 21, the ridges 11d and 21d are typically chamfered to prevent chipping, etc. Therefore, the ridges 11d and 21d of the ceramic bodies 11 and 21 are formed to be rounded.

[0077] 11(B), the Y-axis direction peripheral edge of the internal electrode of the capacitance forming portion 28 is not rounded, and therefore the cross section of the capacitance forming portion 28 is configured to be substantially rectangular. That is, the capacitance forming portion 28 includes a first linear portion 281 extending in the Y-axis direction, a second linear portion 282 extending in the Z-axis direction, and a corner portion 283 bent at a substantially right angle.

[0078] As a result, in the ceramic body 21, the distance from the rounded ridge 21d on the surface to the corner 283 formed by the end of the outermost internal electrode tends to be small. Therefore, particularly when the side margin portion 27 is configured to be thin in the Y-axis direction, the distance between the ridge 21d and the outermost internal electrode becomes small. Therefore, moisture easily penetrates from the vicinity of the ridge 21d, and moisture resistance decreases.

[0079] 11(A), the capacitance forming portion 18 includes a corner 183 that is curved so as to satisfy a≧1 μm and a / b≧0.1. This makes it possible to ensure a sufficient distance from the edge portion 11d of the ceramic body 11 to the peripheral edge E2 of the outermost internal electrode E. This makes it possible to suppress a decrease in moisture resistance due to the thinning of the side margin portion 17.

[0080] 10, when the corner 183 satisfies a≧1 μm, a sufficient distance can be ensured from the main surface 16c to the tip Ea2 of the outermost internal electrode E. In this embodiment, the side margin 17 is added later, so the boundary between the laminate 16 and the side margin 17 is likely to become a path for moisture to penetrate. On the other hand, in this embodiment, the distance in the Z-axis direction from the boundary between the main surface 16c and the side margin 17 to the tip Ea2 can be increased according to the value of a. Therefore, when the corner 183 satisfies a≧1 μm, the above distance can be ensured sufficiently, and moisture resistance to moisture penetration from the main surface 16c side can also be improved.

[0081] Furthermore, by satisfying the condition a / b≦0.4 for the corner 183, the peripheral edge E2 of the outermost internal electrode E can be prevented from curving too sharply in the Z-axis direction. As described above, the peripheral edges 12b, 13b of the internal electrodes 12, 13 tend to curve more sharply inward in the Z-axis direction as they are disposed further outward in the Z-axis direction. Therefore, if the outermost internal electrode E is curved sharply, the peripheral edge E2 may come into contact with the peripheral edges 12b, 13b adjacent to it in the Z-axis direction, resulting in a short circuit. By satisfying the condition a / b≦0.4 for the corner 183, the curvature of the peripheral edge E2 can be moderated, preventing a short circuit due to contact between the internal electrodes 12, 13.

[0082] As described above, the multilayer ceramic capacitor 10 of this embodiment can improve moisture resistance and also suppress short circuits between the internal electrodes 12, 13, thereby improving reliability.

[0083] The laminated chip 116 before firing may also have a first linear portion, a second linear portion, and a corner portion similar to the capacitance forming portion 18 in a cross section that bisects the capacitance forming portion 118 in the X-axis direction and is perpendicular to the X-axis direction, and the corner portion may be curved to satisfy the conditions a≧1 μm and 0.1≦a / b≦0.4. This allows the firing process in step S05 to form a corner portion 183 that satisfies the above conditions. Hereinafter, this embodiment will be further described with reference to examples.

[0084] [Example] As examples and comparative examples of this embodiment, samples of multilayer ceramic capacitors having capacitance forming portions with various cross-sectional shapes were fabricated and their reliability was examined. In these samples, the dimension in the X-axis direction was 1.0 mm, and the dimensions in the Y-axis direction and Z-axis direction were 0.5 mm. The thickness dimension in the Y-axis direction of the side margin portion was 10 μm.

[0085] The values ​​of a and b of the corners of the capacitance-forming portion measured for each example and comparative example of the multilayer ceramic capacitor, and the value of a / b calculated from these values, are shown in Table 1. Note that the values ​​shown in Table 1 are all average values ​​for 1000 samples for each example and comparative example.

[0086] [Table 1]

[0087] The value a corresponds to the height dimension of the corner portion along the Z-axis direction. That is, as shown in FIG. 10, a is the distance between the first imaginary line (L1) extended from the first straight line portion (181) and the second imaginary line (L2). This is the distance along the Z-axis direction between the end point (P2) of the line portion (182) on the first virtual line (L1) side and the end point (P2) of the line portion (182).

[0088] The value b corresponds to the length of the corner along the Y-axis direction. That is, as shown in Fig. 10, b is the distance along the Y-axis direction between the second imaginary line (L2) to which the second straight line portion (182) is extended and the end point (P1) of the first straight line portion (181) on the second imaginary line (L2) side.

[0089] As shown in Table 1, the corners of the samples of Examples 1 to 4 all satisfied the conditions a≧1 μm and 0.1≦a / b≦0.4.

[0090] On the other hand, the sample of Comparative Example 1 had a of 0.2 μm and a / b of 0.01, which did not satisfy the conditions of a≧1 μm and a / b≧0.1. In the sample of Comparative Example 2, a was 1 μm, but a / b was 0.03, which did not satisfy the condition a / b≧0.1. In all of the samples of Comparative Examples 3 to 8, the a / b ratio was 0.50 or more, and did not satisfy the condition of a / b≦0.4.

[0091] The moisture degradation rate was measured for 1,000 samples for each of Examples 1 to 4 and Comparative Examples 1 to 8. The moisture degradation rate was calculated from the percentage of samples whose insulation resistance was less than 1 MΩ after applying a voltage twice the rated voltage for 100 hours at a temperature of 85°C and a humidity of 85% and then measuring the insulation resistance.

[0092] In Examples 1 to 4 and Comparative Examples 3 to 8, in which the corners satisfied the conditions of a≧1 μm and a / b≧0.1, the moisture resistance degradation rate was 0.0%, confirming that the samples had sufficient moisture resistance.

[0093] On the other hand, in Comparative Example 1 where a was 0.2 μm and a / b was 0.01, the moisture resistance deterioration rate was 0.5%, and it was confirmed that the moisture resistance was inferior to that of the Examples. Furthermore, in Comparative Example 2 where a was 1.0 μm and a / b was 0.03, the moisture resistance deterioration rate was 0.1%, and it was confirmed that the moisture resistance was slightly inferior to that of the Examples.

[0094] Next, the short circuit defect rate of each sample was evaluated. The evaluation of the short circuit defect rate was carried out using an LCR meter under the conditions of applying a voltage with an Osc (Oscillation level) of 0.5 V and a frequency of 1 kHz. For each sample, 100 randomly selected samples were evaluated, and the percentage of samples that had short circuits out of the 100 was taken as the short circuit defect rate.

[0095] As a result, the short circuit defect rate was 0% in Examples 1 to 4 and Comparative Examples 1 and 2, which satisfied a / b≦0.4. Therefore, it was confirmed that in Examples 1 to 4, which satisfied the above conditions, the peripheral edges of the internal electrodes were not curved so sharply that they came into contact with adjacent internal electrodes, and short circuits could be prevented.

[0096] On the other hand, in Comparative Examples 3 to 8, where a / b was greater than 0.4, the short circuit defect rate was 1% or more. In particular, there was a tendency for the short circuit defect rate to increase as a / b increased. From these results, it was confirmed that short circuits can be reliably suppressed by keeping a / b at 0.4 or less.

[0097] From the above, it was confirmed that all of Examples 1 to 4, in which the corners satisfy the conditions of a≧1 μm and 0.1≦a / b≦0.4, have a highly reliable configuration with high moisture resistance and suppressed short circuits.

[0098] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the gist of the present invention.

[0099] Furthermore, although the above embodiment has described the multilayer ceramic capacitor 10 as an example of a multilayer ceramic electronic component, the present invention is applicable to all multilayer ceramic electronic components having a ceramic element body in which internal electrodes are laminated. Examples of such multilayer ceramic electronic components include chip varistors, chip thermistors, and multilayer inductors. [Explanation of symbols]

[0100] 10...Multilayer ceramic capacitors (multilayer ceramic electronic components) 12,13…Internal electrode 17...Side margin 18...Capacity formation part (functional part) 19...Cover part 181...1st straight section 182…Second straight section 183...Corner

Claims

1. a functional section having a plurality of internal electrodes stacked in a first direction; a cover portion that covers the functional portion from the first direction; a side margin portion covering the functional portion from a second direction perpendicular to the first direction; The element includes: the functional portion bisects the functional portion in a third direction perpendicular to the first direction and the second direction, and in a cross section perpendicular to the third direction, has: a first linear portion in contact with the cover portion and extending in the second direction; a second linear portion in contact with the side margin portion and extending in the first direction; and a corner portion connecting the first linear portion and the second linear portion; the corner portion is curved so as to satisfy the conditions of 2 μm≦a≦10 μm and 0.1≦a / b≦0.4, where a is a distance along the first direction between a first virtual line along which the first straight line portion is extended in the second direction and an end point of the second straight line portion on the side of the first virtual line, and b is a distance along the second direction between a second virtual line along which the second straight line portion is extended in the first direction and an end point of the first straight line portion on the side of the second virtual line, an internal electrode included in the functional unit is flat from one end along the third direction to the other end along the third direction on a side surface of the functional unit facing the second direction or on a cross section perpendicular to the second direction; the positions of the ends of the plurality of internal electrodes in the second direction are aligned along the first direction with a variation in the second direction of 0.5 μm or less; Multilayer ceramic electronic components.

2. 2. The multilayer ceramic electronic component according to claim 1, Among the internal electrodes included in the functional portion, at least the outermost internal electrode includes a flat portion constituting the first linear portion, and a peripheral portion located on a peripheral edge of the flat portion in the second direction and curved inward from the flat portion in the first direction. Multilayer ceramic electronic components.

3. 3. The multilayer ceramic electronic component according to claim 1, a distance b along the second direction between the second virtual line and an end point of the first straight line portion on the second virtual line side is 10% or less of a dimension of the element body along the second direction; Multilayer ceramic electronic components.

4. 4. The multilayer ceramic electronic component according to claim 1, The thickness of the side margin portion is 10 μm or more and 15 μm or less. Multilayer ceramic electronic components.

5. 5. The multilayer ceramic electronic component according to claim 4, The thickness of the side margin portion is 12 μm or less. Multilayer ceramic electronic components.

6. 6. The multilayer ceramic electronic component according to claim 1, The corner portion curves inward in the first direction from the end point of the first straight line portion on the second imaginary line side toward the end point of the second straight line portion on the first imaginary line side. Multilayer ceramic electronic components.

7. 7. The multilayer ceramic electronic component according to claim 1, The functional portion has four corners in the cross section. Multilayer ceramic electronic components.

8. 8. The multilayer ceramic electronic component according to claim 1, The distance b is 20 μm≦b≦25 μm. Multilayer ceramic electronic components.

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