Multilayer ceramic electronic component

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 multilayer ceramic electronic components such as multilayer ceramic capacitors and a method for manufacturing the same.

Background Art

[0002] In recent years, with the miniaturization and high performance of electronic devices, the demand for miniaturization and large capacitance of multilayer ceramic capacitors used in electronic devices has been increasing. To meet this demand, it is effective to expand the internal electrodes of multilayer ceramic capacitors. To expand the internal electrodes, it is necessary to thin the side margin portion for ensuring the insulation around the internal electrodes.

[0003] Patent Document 1 discloses a technique of attaching the side margin portion later in view of thinning the side margin portion. In this technique, a ceramic protective layer (side margin portion) 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

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the technique described in Patent Document 1, when the side margin portion is thinned, sufficient moisture resistance cannot be obtained, and it is difficult to improve the reliability.

[0006] In view of the above circumstances, an object of the present invention is to provide a multilayer ceramic electronic component capable of improving the reliability and a method for manufacturing the same.

Means for Solving the Problems

[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 portion has internal electrodes laminated 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 orthogonal to the first direction. The functional portion bisects the functional portion in a third direction orthogonal to the first direction and the second direction, and in a cross section orthogonal to the third direction, a first straight portion that extends in the second direction and is in contact with the cover portion, a second straight portion that extends in the first direction and is in contact with the side margin portion, 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 obtained by extending the first straight portion in the second direction and an end point of the second straight portion on the first virtual line side is a, and the distance along the second direction between a second virtual line obtained by extending the second straight portion in the first direction and an end point of the first straight portion on the second virtual line side is b, it curves so as to satisfy the conditions of a ≧ 1 μm and 0.1 ≦ a / b ≦ 0.4.

[0008] In this configuration, the functional portion has a corner portion that curves so that a ≧ 1 μm and 0.1 ≦ a / b ≦ 0. Because the corner portion satisfies the conditions of a ≧ 1 μm and a / b ≧ 0.1, the distance from the surface of the multilayer ceramic electronic component to the end of the outermost internal electrode can be sufficiently ensured, and deterioration due to moisture resistance can be suppressed. In addition, by satisfying the condition of a / b ≦ 0.4 for the corner portion, it is possible to prevent the outermost internal electrode from curving steeply. Thereby, a short circuit between adjacent internal electrodes in the first direction can be suppressed. Therefore, according to the above configuration, deterioration due to moisture resistance and short circuit defects can be suppressed, and a highly reliable multilayer ceramic electronic component can be obtained.

[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. Thereby, even when the thickness of the side margin portion is very thin, sufficient moisture resistance can be ensured. Therefore, a small-sized and large-capacity laminated ceramic electronic component with high reliability can be obtained.

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

[0011] Specifically, the functional portion may have four such corner portions in the cross section.

[0012] A method for manufacturing a laminated ceramic electronic component according to another aspect of the present invention includes a step of producing a laminated sheet by laminating a third ceramic sheet having no internal electrode formed thereon in the first direction on the outer surface in the first direction of a laminate in which a first ceramic sheet and a second ceramic sheet each having a plurality of internal electrodes formed thereon are alternately laminated 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 portion having internal electrodes laminated in the first direction, a cover portion covering the functional portion from the first direction, and a side surface where the internal electrodes are exposed and facing in a second direction orthogonal to the first direction, the functional portion bisects the functional portion in a third direction orthogonal to the first direction and the second direction, and in a cross section orthogonal to the third direction, is in contact with the cover portion and extends in the second direction a first straight line portion, a second straight line portion in contact with the side margin portion and extending in the first direction, and a corner portion connecting the first straight line portion and the second straight line portion. When the distance along the first direction between the first virtual line obtained by extending the first straight line portion in the second direction and the end point of the second straight line portion on the first virtual line side is a, and the distance along the second direction between the second virtual line obtained by extending the second straight line portion in the first direction and the end point of the first straight line portion on the second virtual line side is b, a ≧ 1 μm and 0.1 ≦ a / b curves so as to satisfy the condition of ≦ 0.4, a multilayer chip is manufactured. A side margin portion is formed on the side surface.

[0013] Also, in the first ceramic sheet and the second ceramic sheet, the plurality of internal electrodes are arranged to be mutually separated in the second direction via non-electrode formation regions. In the step of pressing from the first direction, a functional region in which the plurality of internal electrodes are laminated in the first direction and an excision region in which the non-electrode formation regions are laminated, adjacent to the functional region in the second direction, and configured such that the thickness in the first direction gradually decreases as the excision region is separated from the functional region in the second direction are formed in the laminated sheet. In the step of cutting the laminated sheet, the excision region is excised. In a region adjacent to the excision region of the functional region, the internal electrode is curved inward in the first direction by pressing. Thereby, a corner portion curved so as to satisfy the above conditions can be formed.

Advantages of the Invention

[0014] As described above, according to the present invention, it is possible to provide a multilayer ceramic electronic component capable of enhancing reliability and a method for manufacturing the same. [[ID=:24]]

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

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

[0017] [Configuration of Multilayer Ceramic Capacitor 10] FIGS. 1 to 3 are diagrams showing a multilayer ceramic capacitor 10 according to an embodiment of the present invention. FIG. 1 is a perspective view of the multilayer ceramic capacitor 10. FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor 10 along the A-A' line of FIG. 1. FIG. 3 is a cross-sectional view of the multilayer ceramic capacitor 10 along the B-B' line of 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 in the Z-axis direction, two end surfaces facing in the X-axis direction, and two side surfaces facing in the Y-axis direction. For example, the ridge portions 11d connecting the respective surfaces of the ceramic body 11 are rounded.

[0019] The external electrodes 14 and 15 cover the end surfaces of the ceramic body 11 and face each other in the X-axis direction with the ceramic body 11 interposed therebetween. The external electrodes 14 and 15 extend from the end surfaces of the ceramic body 11 to the main surfaces and the side surfaces. As a result, in the external electrodes 14 and 15, both the cross section parallel to the X-Z plane and the cross section parallel to the X-Y plane are U-shaped. Note that the shape of the external electrodes 14 and 15 is not limited to that shown in FIG. 1.

[0020] The external electrodes 14 and 15 are formed of a good electrical conductor. Examples of the good electrical conductor forming the external electrodes 14 and 15 include metals or alloys mainly composed of copper (Cu), nickel (Ni), tin (Sn), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), and the like.

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

[0022] The side margin portion 17 covers the two side surfaces 16b of the laminate 16, and covers the capacitance forming portion 18 from the Y-axis direction. The thickness dimension of the side margin portion 17 in the Y-axis direction can be, for example, 15 μm or less, more preferably 12 μm or less. Thereby, miniaturization and increased capacitance of the multilayer ceramic capacitor 10 can be achieved. Further, the thickness dimension of the side margin portion 17 in the Y-axis direction can be, for example, 10 μm or more. Thereby, the moisture resistance of the multilayer ceramic capacitor 10 can be ensured. Note that the thickness dimension of the side margin portion 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 laminated via a ceramic layer in the Z-axis direction. The capacitance forming portion 18 is configured as a functional portion in the present embodiment.

[0024] The internal electrodes 12 and 13 are each configured as a sheet extending along the X-Y 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. Thereby, when a voltage is applied between the first external electrode 14 and the second external electrode 15, a voltage is applied to the ceramic layer between the first internal electrode 12 and the second internal electrode 13, and charges corresponding to the voltage are stored in the capacitance forming portion 18.

[0025] The internal electrodes 12 and 13 are formed of a good electrical conductor. Typical examples of the good electrical conductor forming the internal electrodes 12 and 13 include nickel (Ni), and other metals or alloys mainly composed of copper (Cu), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), etc. may also be mentioned.

[0026] In the ceramic body 11, a dielectric ceramic with a high dielectric constant is used to increase the capacitance of each ceramic layer between the internal electrodes 12 and 13. Examples of the dielectric ceramic with a high dielectric constant include materials having a perovskite structure containing barium (Ba) and titanium (Ti), typified by barium titanate (BaTiO3).

[0027] Note that the ceramic layer may be composed of a strontium titanate (SrTiO3) - based, calcium titanate (CaTiO3) - based, magnesium titanate (MgTiO3) - based, calcium zirconate (CaZrO3) - based, calcium zirconate titanate (Ca(Zr,Ti)O3) - based, barium zirconate (BaZrO3) - based, titanium oxide (TiO2) - based material, etc.

[0028] The cover portion 19 and the side margin portion 17 are formed of an insulating ceramic, but may contain, for example, the dielectric ceramic used in the capacitance forming portion 18. Thereby, the internal stress that may occur between the cover portion 19 and the side margin portion 17 and the capacitance forming portion 18 is suppressed.

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

[0030] [Manufacturing method of 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. Hereinafter, the method for manufacturing the multilayer ceramic capacitor 10 will be described with reference to FIGS. 5 to 9 as appropriate along FIG. 4.

[0031] (Step S01: Ceramic sheet lamination) 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 laminated.

[0032] The ceramic sheets 101, 102, 103 are configured as unfired dielectric green sheets mainly composed of dielectric ceramics. The ceramic sheets 101, 102, 103 are formed into a sheet shape using, for example, a roll coater or a doctor blade. The thickness of the ceramic sheets 101, 102, 103 can be adjusted as appropriate.

[0033] FIG. 5 is a plan view of the ceramic sheets 101, 102. At this stage, the ceramic sheets 101, 102 are configured as large-sized sheets that have not been separated into individual pieces. In FIG. 5, cutting lines Lx1, Lx2, Ly1, Ly2 for separating into individual multilayer ceramic capacitors 10 are shown. The cutting lines Lx1, Lx2 are parallel to the X-axis, and the cutting lines Ly1, Ly2 are parallel to the Y-axis. The intermediate line Lc is a virtual line extending at a position that bisects the space between adjacent cutting lines Lx1, Lx2.

[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 and 113 can be formed by applying an arbitrary conductive paste to the ceramic sheets 101 and 102. The method of applying the conductive paste can be arbitrarily selected from known techniques. For example, for applying the conductive paste, a screen printing method or a gravure printing method can be used.

[0036] In the first ceramic sheet 101, a first row in which the internal electrode 112 extending across the cutting line Ly1 is arranged along the X-axis direction and a second row in which the internal electrode 112 extending across the cutting line Ly2 is 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 with the cutting line Ly2 therebetween. In the second row, the internal electrodes 112 adjacent to each other in the X-axis direction face each other with the cutting line Ly1 therebetween. 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 shifted by one chip in the X-axis direction. Each first internal electrode 112 is arranged with the intermediate line Lc therebetween 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 electrode 113 on the second ceramic sheet 102 is also configured in the same manner as the internal electrode 112. However, in the second ceramic sheet 102, the internal electrode 113 in the row corresponding to the first row of the first ceramic sheet 101 extends across the cutting line Ly2, and the internal electrode 113 in the row corresponding to the second row of the first ceramic sheet 101 extends across the cutting line Ly1. That is, the internal electrode 113 is formed shifted by one chip in the X-axis direction or the Y-axis direction from the internal electrode 112. Each second internal electrode 113 is arranged with the intermediate line Lc therebetween in the Y-axis direction. The outer edges of each second internal electrode 113 in the Y-axis direction extend along the cutting lines Lx1 and Lx2.

[0038] On the first ceramic sheet 101, non-electrode forming regions N1 where the internal electrodes 112 are not applied are formed in a lattice pattern on the intermediate line Lc and the cutting line Ly2. Similarly, on the second ceramic sheet 102, non-electrode forming regions N2 where the internal electrodes 113 are not applied are formed in a lattice pattern on the intermediate line Lc and the cutting line Ly1. That is, on the intermediate line Lc between the cutting lines Lx1 and Lx2, the non-electrode forming regions N1 and N2 of both are configured to overlap.

[0039] These ceramic sheets 101, 102, and 103 are laminated as shown in FIG. 6 to produce a laminated sheet 104. Specifically, the first ceramic sheet 101 and the second ceramic sheet 102 are laminated alternately, and the third ceramic sheet 103 is laminated on the upper and lower surfaces in the Z-axis direction of the laminate of the ceramic sheets 101 and 102. In the example shown in FIG. 6, four third ceramic sheets 103 are laminated respectively, but the number of the third ceramic sheets 103 can be changed as appropriate.

[0040] (Step S02: Pressing) In step S02, the laminated sheet 104 is pressed from the Z-axis direction.

[0041] FIG. 7 is a schematic cross-sectional view of the laminated sheet 104 as viewed from the X-axis direction for explaining the pressing process of step S02. In the pressing process of this step, a pair of pressing plates S1 are opposed to sandwich the laminated sheet 104 in the Z-axis direction, and the laminated sheet 104 is pressed by pressing these pressing plates S1 toward the laminated sheet 104. The pressing plates S1 are pressed, for example, by hydrostatic pressure or uniaxial pressure.

[0042] Furthermore, an elastic sheet S2 is disposed between the pressing plate S1 and the laminated sheet 104. The elastic sheet S2 is composed of a sheet-like elastic body and is formed, for example, of polyethylene terephthalate (PET) resin. The elastic sheet S2 is pressed toward the laminated sheet 104 by the pressing plate S1.

[0043] In the stacked sheet 104, a capacitance forming region (functional region) 105 in which both of the internal electrodes 112 and 113 are stacked, and a cutting region 106 in which both of the non-electrode forming regions N1 and N2 are stacked are formed. The capacitance forming region 105 corresponds to the capacitance forming portion 18 and the cover portion 19 covering the upper and lower sides thereof. The cutting region 106 is a region adjacent to the capacitance forming region 105 in the Y-axis direction and in which the internal electrodes 112 and 113 are not stacked. That is, the cutting region 106 is a region sandwiched between the cutting lines Lx1 and Lx2 and is cut in a cutting process described later.

[0044] At the time of pressure bonding, the thickness in the Z-axis direction in the cutting region 106 of the elastic sheet S2 becomes thicker than the thickness in the Z-axis direction of the capacitance forming region 105. By pressing such a stacked sheet 104 with the elastic sheet S2 interposed therebetween, a cutting region 106 having a shape sunken inward in the Z-axis direction can be formed as 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 a gap. As a result, the capacitance forming region 105 is substantially uniformly compressed while being extended in the X-Y plane as a whole by the pressure bonding process. As a result, a substantially flat surface is formed on the capacitance forming region 105.

[0046] On the other hand, a gap corresponding to the non-electrode forming regions N1 and N2 is formed in the cutting region 106 before pressure bonding. Further, the green sheet is softer and easier to extend than the internal electrodes 112 and 113. Therefore, due to the pressure bonding, the green sheet extended from the capacitance forming region 105 enters the gap.

[0047] Furthermore, the elastic sheet S2 is disposed thicker than the capacitance forming region 105 in the excision region 106, and sufficient load can be applied to the excision region 106 with a small thickness even by elastic deformation. As a result, in the excision region 106, the green sheet extended from the capacitance forming region 105 and the green sheet laminated before pressing are pressure-bonded in the Z-axis direction while extending in the X-Y plane. Therefore, in the excision region 106, the thickness between the internal electrodes 12 and 13 gradually decreases from the cutting lines Lx1 and Lx2 on the capacitance forming region 105 side toward the intermediate line Lc. That is, the excision region 106 is configured such that the thickness in the Z-axis direction gradually decreases as it separates from the capacitance forming region 105 in the Y-axis direction. As a result, the excision region 106 is formed to largely sink inward in the Z-axis direction near the intermediate line Lc.

[0048] In response to the sinking of the excision region 106, the peripheral portions 112b and 113b of the internal electrodes 112 and 113 adjacent to the excision region 106 also curve inward in the Z-axis direction. More specifically, the peripheral portions 112b and 113b receive a force inward in the Z-axis direction by the elastic sheet S2 biting into the excision region 106 and curve. In addition, the peripheral portions 112b and 113b can also receive a force inward in the Z-axis direction by the laminate of the ceramic sheets 103 extended from the central portion side of the capacitance forming region 105. As a result, the curved peripheral portions 112b and 113b are formed on the internal electrodes 112 and 113. The internal electrodes 112 and 113 located more outward in the Z-axis direction are more likely to receive a force inward in the Z-axis direction, so they curve more greatly inward in the Z-axis direction.

[0049] In FIGS. 8 to 9, the region outside the peripheral portions 112b and 113b on the main surface facing the Z-axis direction is described as substantially flat, but this region may curve inward in the Z-axis direction in the same manner as the peripheral portions 112b and 113b.

[0050] (Step S03: Cutting) In step S03, the laminated sheet 104 crimped in step S02 is cut along the cutting lines Lx1, Lx2, Ly1, and Ly2 to produce the unfired laminated chip 116 shown in FIG. 8. The laminated chip 116 corresponds to the laminated body 16 after firing. For cutting the laminated sheet 104 in this step, for example, a punching blade or a rotary blade can be used.

[0051] When cutting the cutting lines Lx1 and Lx2 with a punching blade, since the width of the blade is relatively narrow, the blade can be brought into contact with each of the cutting lines Lx1 and Lx2 for cutting. As a result, the laminated sheet 104 is cut at each of the cutting lines Lx1 and Lx2, and the excision region 106 between the cutting lines Lx1 and Lx2 is removed, thereby forming each laminated chip 116.

[0052] When cutting the cutting lines Lx1 and Lx2 with a rotary blade, since the width of the blade is relatively wide, the blade is brought into contact with the entire excision region 106 including the cutting lines Lx1 and Lx2. As a result, the excision region 106 is excised by the rotary blade, and each laminated chip 116 is formed.

[0053] As shown in FIG. 8, on the laminated chip 116, a side surface 116b is formed as a cut surface corresponding to the cutting lines Lx1 and Lx2. From the side surface 116b, the peripheral edges 112b and 113b of the internal electrodes 112 and 113 are exposed. The peripheral edges 112b and 113b curve inward in the Z-axis direction as they approach the side surface 116b. On the other hand, on the laminated chip 116, an end surface 116a is formed as a cut surface corresponding to the cutting lines Ly1 and Ly2. From the end surface 116a, one of the internal electrodes 112 and 113 is exposed.

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

[0055] (Step S04: Side margin portion formation) In step S04, an unfired side margin portion 117 is formed on the side surface 116b where the internal electrodes 112 and 113 in the laminated chip 116 obtained in step S03 are exposed. Thereby, an unfired ceramic green body 111 as shown in FIG. 9 is produced.

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

[0057] (Step S05: Firing) In step S05, the unfired ceramic green 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 green body 111. Also, the firing can be performed, for example, in a reducing atmosphere or in a low oxygen partial pressure atmosphere.

[0058] (Step S06: Barrel polishing) In step S06, the fired ceramic green body 111 is barrel polished. The barrel polishing is performed, for example, by enclosing a plurality of ceramic green bodies 111 in a barrel container and applying rotation or vibration to the barrel container. The barrel container may be enclosed with a polishing medium and a liquid together with a plurality of ceramic green bodies 111. Thereby, the ridge portion 11d connecting between the respective surfaces of the ceramic green body 111 is chamfered, and the ceramic green body 11 shown in FIGS. 1 to 3 is produced.

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

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

[0061] Note that a part of the process in step S07 may be performed before step S05. For example, an unfired electrode material may be applied to both end faces of the unfired ceramic body 111 in the X-axis direction before step S05, and in step S05, while firing the unfired ceramic body 111, the unfired electrode material may be baked to form an underlayer of the external electrodes 14 and 15. Also, an unfired electrode material may be applied to the ceramic body 111 that has undergone the debinding process, and these may be fired simultaneously.

[0062] Thus, the multilayer ceramic capacitor 10 is completed. In this manufacturing method, since the side margin portion 17 is retrofitted to the side surface 16b of the laminate 16 where the internal electrodes 12 and 13 are exposed, the positions of the ends of the plurality of internal electrodes 12 and 13 in the ceramic body 11 in the Y-axis direction are aligned along the Z-axis direction with a variation within 0.5 μm.

[0063] Also, the fired internal electrodes 12 and 13 are formed with curved peripheral portions 12b and 13b corresponding to the peripheral portions 112b and 113b. Due to this peripheral portion 12b and 13b, the capacitance forming portion 18 has a cross-sectional shape as described below.

[0064] [Detailed configuration of capacitance forming portion 18] The capacitance forming portion 18 is divided into two equal parts in the X-axis direction, and is configured in a rounded rectangular shape in a cross section orthogonal to the X-axis direction (a cross section along the B-B' line). The cross section along the B-B' line is hereinafter referred to as the "B-B' cross section".

[0065] As shown in FIG. 3, in the above cross section, the capacitance forming portion 18 has two first straight portions 181 that are in contact with the cover portion 19 and extend in the Y-axis direction, two second straight portions 182 that are in contact with the side margin portion 17 and extend in the Z-axis direction, and four corner portions 183 that connect the first straight portion 181 and the second straight portion 182. The two first straight portions 181 face each other in the Z-axis direction, and the two second straight 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-symmetric with respect to the Y-axis direction and the Z-axis direction. Therefore, hereinafter, with reference to FIG. 10, which is an enlarged cross-sectional view of FIG. 3, the configuration of one corner portion 183 and the first straight portion 181 and the second straight portion 182 connected thereto will be described in detail.

[0067] As shown in FIG. 10, the first straight portion 181 is a straight portion extending in the Y-axis direction and is composed of the innermost internal electrodes 12 and 13 in the Z-axis direction. Note that the first straight portion 181 only needs to be substantially straight, and for example, it may meander or bend in the Z-axis direction within a slight range within 1% of the height dimension of the ceramic element 11 in the Z-axis direction.

[0068] The outermost internal electrodes 12 and 13 are referred to as the outermost internal electrode E. The outermost internal electrode E includes a flat portion E1 that constitutes the first straight portion 181 and a peripheral portion E2 that is located at the peripheral edge 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 for example, it may have irregularities in the Z-axis direction within a slight range within 1% of the height dimension of the ceramic element 11 in the Z-axis direction. The end point P1 of the first straight portion 181 is located at the boundary between the flat portion E1 and the peripheral portion E2.

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

[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 the corner portion 183 is defined by the following values of a and a / b. a is a value corresponding to the height dimension along the Z-axis direction of the corner portion 183, and b is a value corresponding to the length dimension along the Y-axis direction of the corner portion 183. Thereby, a preferable shape of the corner portion 183 is defined.

[0072] More specifically, a is the distance along the Z-axis direction between the first virtual line L1 extended from the first straight portion 181 and the end point P2 on the first virtual line L1 side of the second straight portion 182. 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, etc. Alternatively, the value of a can also be controlled by the elastic modulus of the elastic sheet S2 and the load applied by the pressure plate S1 in the crimping process of step S02 described above.

[0073] b is the distance along the Y-axis direction between the second virtual line L2 extended from the second straight portion 182 and the end point P1 on the second virtual line L2 side of the first straight portion 181. The value of b can be controlled not only by the number of laminated ceramic sheets 101, 102 or the thickness of the ceramic sheets 101, 102, etc., but also by the elastic modulus of the elastic sheet S2 and the load applied by the pressure plate S1 in the crimping process of step S02 described above.

[0074] The corner portion 183 is curved so as to satisfy the conditions of a ≧ 1 μm and 0.1 ≦ a / b ≦ 0.4. Among the above conditions, when the corner portion 183 satisfies a ≧ 1 μm and a / b ≧ 0.1, the peripheral edge portion E2 of the outermost layer internal electrode E can be sufficiently curved, and the moisture resistance can be enhanced as shown below.

[0075] FIG. 11(A) is a diagram schematically showing a cross section taken along the line B - B' of the ceramic element 11 according to the present embodiment, and the region occupied by the capacitance forming portion 18 is surrounded by a broken line. FIG. 11(B) is a diagram schematically showing a cross section taken along the line B - B' of the ceramic element 21 according to the comparative example of the present embodiment, and the region occupied by the capacitance forming portion 28 is surrounded by a broken line.

[0076] In the ceramic elements 11 and 21, typically, from the viewpoint of preventing defects and the like, the ridge portions 11d and 21d are chamfered. For this reason, the ridge portions 11d and 21d of the ceramic elements 11 and 21 are formed with rounded edges.

[0077] In the ceramic element 21 of the comparative example according to FIG. 11(B), since the peripheral edge portion of the internal electrode of the capacitance forming portion 28 in the Y - axis direction is not rounded, the cross - sectional shape of the capacitance forming portion 28 is configured in a substantially rectangular shape. That is, the capacitance forming portion 28 includes a first straight portion 281 extending in the Y - axis direction, a second straight portion 282 extending in the Z - axis direction, and a corner portion 283 that bends at a substantially right angle.

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

[0079] On the other hand, in the ceramic element 11 of the present embodiment according to FIG. 11(A), the capacitance forming portion 18 includes a corner portion 183 that is curved so as to satisfy a ≧ 1 μm and a / b ≧ 0.1. As a result, it becomes possible to sufficiently secure the distance from the ridge portion 11d of the ceramic element 11 to the peripheral edge portion E2 of the outermost layer internal electrode E. Therefore, it is possible to suppress a decrease in moisture resistance accompanying thinning of the side margin portion 17.

[0080] Also, referring to FIG. 10, by the corner portion 183 satisfying a ≧ 1 μm, it is possible to sufficiently secure the distance from the main surface 16c to the tip portion Ea2 of the outermost layer internal electrode E. In the present embodiment, since the side margin portion 17 is attached later, the boundary portion between the laminate 16 and the side margin portion 17 is likely to be a moisture ingress path. On the other hand, in the present embodiment, the distance in the Z-axis direction from the boundary portion between the main surface 16c and the side margin portion 17 to the tip portion Ea2 can be increased according to the value of a. Therefore, by the corner portion 183 satisfying a ≧ 1 μm, the above distance can be sufficiently secured, and the moisture resistance against moisture ingress from the main surface 16c side can also be enhanced.

[0081] Furthermore, by the corner portion 183 satisfying the condition of a / b ≦ 0.4, it is possible to prevent the peripheral edge portion E2 of the outermost layer internal electrode E from being too steeply curved in the Z-axis direction. As described above, the peripheral edge portions 12b, 13b of the internal electrodes 12, 13 have a tendency to be more steeply curved inward in the Z-axis direction as they are arranged more outward in the Z-axis direction. Therefore, when the outermost layer internal electrode E is steeply curved, there is a possibility that the peripheral edge portion E2 and the peripheral edge portions 12b, 13b adjacent in the Z-axis direction come into contact and short-circuit. By the corner portion 183 satisfying the condition of a / b ≦ 0.4, the curvature of the peripheral edge portion E2 can be moderately relaxed, and a short circuit due to contact between the internal electrodes 12, 13 can be prevented.

[0082] Thus, according to the multilayer ceramic capacitor 10 of the present embodiment, it is possible to enhance moisture resistance, suppress short circuits between the internal electrodes 12, 13, and enhance reliability.

[0083] Note that the laminated chip 116 before firing also bisects the capacitance forming portion 118 in the X-axis direction, and in a cross-section orthogonal to the X-axis direction, it has a first straight portion, a second straight portion, and a corner portion similar to the capacitance forming portion 18, and the corner portion may be curved so as to satisfy the conditions of a≧1μm and 0.1≦a / b≦0.4. Thereby, in the firing step of step S05, the corner portion 183 satisfying the above conditions can be formed. Hereinafter, the present embodiment will be further described with reference to examples.

[0084] [Examples] As examples and comparative examples of the present 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, the dimensions in the Y-axis direction and the Z-axis direction were 0.5 mm. Also, the thickness dimension of the side margin portion in the Y-axis direction was 10 μm.

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

[0086]

Table 1

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

[0088] b is a value corresponding to the length dimension along the Y-axis direction of the above-mentioned corner portion. That is, as shown in FIG. 10, b is the distance along the Y-axis direction between the second virtual line (L2) to which the second straight line portion (182) is extended and the end point (P1) on the second virtual line (L2) side of the first straight line portion (181).

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

[0090] On the other hand, the sample of Comparative Example 1 had a = 0.2 μm and a / b = 0.01, and did not satisfy the conditions of a ≥ 1 μm and a / b ≥ 0.1. Also, the sample of Comparative Example 2 had a = 1 μm, but a / b = 0.03, and did not satisfy the condition of a / b ≥ 0.1. The samples of Comparative Examples 3 to 8 all had a / b ≥ 0.50 and did not satisfy the condition of a / b ≤ 0.4.

[0091] For 1000 samples each of these Examples 1 to 4 and Comparative Examples 1 to 8, the moisture resistance deterioration rate was examined. The moisture resistance deterioration rate was calculated from the ratio of the number of samples whose insulation resistance became less than 1 MΩ after applying a voltage twice the rated voltage at a temperature of 85°C and a humidity of 85% for 100 hours and then measuring the insulation resistance.

[0092] In Examples 1 to 4 and Comparative Examples 3 to 8 where the corner portion satisfied the conditions of a ≥ 1 μm and a / b ≥ 0.1, it was confirmed that the moisture resistance deterioration rate was 0.0% in all cases, indicating sufficient moisture resistance.

[0093] On the other hand, in Comparative Example 1 where a = 0.2 μm and a / b = 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. Also, in Comparative Example 2 where a = 1.0 μm and a / b = 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] Subsequently, the short circuit failure rate of each sample was evaluated. The evaluation of the short circuit failure rate was performed under the condition of applying a voltage with Osc (Oscillation level) of 0.5 V and a frequency of 1 kHz using an LCR meter. For each sample, 100 randomly selected evaluations were conducted, and the ratio of the number of samples in which a short circuit occurred out of 100 was defined as the short circuit failure rate.

[0095] As a result, in Examples 1 to 4 and Comparative Examples 1 and 2 that satisfy a / b ≤ 0.4, the short circuit failure rate was 0%. Therefore, in Examples 1 to 4 that satisfy the above conditions, it was confirmed that the peripheral portion of the internal electrode was not curved steeply enough to contact the adjacent internal electrode, and short circuits could be prevented.

[0096] On the other hand, in Comparative Examples 3 to 8 where a / b is greater than 0.4, the short circuit failure rate was 1% or more in all cases. In particular, as a / b increased, the short circuit failure rate tended to increase. From this result, 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 Examples 1 to 4 in which the corners satisfy the conditions of a ≥ 1 μm and 0.1 ≤ a / b ≤ 0.4 all have a highly reliable structure 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 only to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

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

Description of Reference Numerals

[0100] 10…Multilayer ceramic capacitor (multilayer ceramic electronic component) 12, 13…Internal electrode 17…Side margin part 18…Capacitance forming part (functional part) 19…Cover part 181…First straight part 182…Second straight part 183…Corner part

Claims

1. A functional part having a plurality of internal electrodes laminated in a first direction, a cover part covering the functional part from the first direction, a side margin part covering the functional part from a second direction orthogonal to the first direction, and a body including the above, the functional part bisects the functional part in a third direction orthogonal to the first direction and the second direction, and in a cross section orthogonal to the third direction, a first straight part in contact with the cover part and extending in the second direction, a second straight part in contact with the side margin part and extending in the first direction, and a corner part connecting the first straight part and the second straight part, the corner part is curved so as to satisfy the conditions of 2 μm ≤ a ≤ 10 μm and 0.1 ≤ a / b ≤ 0.4, where a is the distance along the first direction between a first virtual line obtained by extending the first straight part in the second direction and an end point of the second straight part on the first virtual line side, and b is the distance along the second direction between a second virtual line obtained by extending the second straight part in the first direction and an end point of the first straight part on the second virtual line side, In a side surface of the functional part facing the second direction or a cross section orthogonal to the second direction, the internal electrodes included in the functional part are flat from one end along the third direction to the other end along the third direction A multilayer ceramic electronic component.

2. [[ID= ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The corner portion curves inward in the first direction from the end point on the second virtual line side of the first straight portion toward the end point on the first virtual line side of the second straight portion. Multilayer ceramic electronic component. Claim 7 The multilayer ceramic electronic component according to any one of claims 1 to 6, The functional portion has four of the corner portions in the cross section. Multilayer ceramic electronic component. Claim 8 The multilayer ceramic electronic component according to any one of claims 1 to 7, The distance b satisfies 20 μm ≤ b ≤ 25 μm. Multilayer ceramic electronic component.

Images