Multilayer ceramic electronic component and manufacturing method thereof

Abstract

To suppress a leakage current from flowing between external electrodes through a surface layer of a ceramic body.SOLUTION: A multilayer ceramic electronic component includes a ceramic body having a capacitance forming portion formed by alternately stacking first internal electrode layers and second internal electrode layers with a dielectric layer sandwiched therebetween, and a protective portion provided around the capacitance forming portion, and external electrodes formed on the surface of the ceramic body so as to be spaced apart from each other, and from which the first internal electrode layers and the second internal electrode layers are extended, respectively, and at least one of the dielectric layers, the first internal electrode layers, the second internal electrode layers, and the external electrodes contains a metal having a melting point below 1100°C as a component, and an oxide of the component is provided in the form of particles in a surface layer portion of the ceramic body between a pair of the external electrodes.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Recently, multilayer ceramic electronic components have been known that include an element body formed by alternately stacking first internal electrode layers and second internal electrode layers with dielectric layers sandwiched therebetween. In the multilayer ceramic electronic component, external electrodes are formed on the surface of the element body so that the electrodes are spaced apart from each other. One of the pair of external electrodes has a first internal electrode layer extending therefrom, and the other external electrode has a second internal electrode layer extending therefrom. In such multilayer ceramic electronic components, so-called leakage current can be a problem. Various proposals have been made to suppress leakage current (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-28224 [Patent Document 2] JP 2019-50410 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, there are various types of leakage current in multilayer ceramic electronic components. For example, leakage current may flow between external electrodes through the surface layer of the ceramic body of the multilayer ceramic electronic component. With regard to such types of leakage current, the proposals disclosed in Patent Documents 1 and 2 leave room for improvement.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to prevent leakage current from flowing between external electrodes through the surface layer of the ceramic body. [Means for solving the problem]

[0006] In order to achieve the above object, a multilayer ceramic electronic component comprises a ceramic body including a capacitance forming portion formed by alternately stacking first internal electrode layers and second internal electrode layers with a dielectric layer sandwiched therebetween, and a protective portion provided around the capacitance forming portion, and external electrodes formed on the surface of the ceramic body so as to be spaced apart from each other, and from which the first internal electrode layers and the second internal electrode layers are extended, respectively, wherein at least one of the dielectric layers, the first internal electrode layers, the second internal electrode layers, and the external electrodes contains a metal having a melting point lower than 1100°C as a component, and an oxide of the component is provided in the form of particles in a surface layer portion of the ceramic body between a pair of the external electrodes.

[0007] In the multilayer ceramic electronic component having the above configuration, the contained component may be copper, and the particulate oxide may be a copper oxide containing cuprous oxide as a main component.

[0008] In the multilayer ceramic electronic component having the above configuration, the contained component may be a main component of at least one of the first internal electrode layers and the second internal electrode layers.

[0009] In the multilayer ceramic electronic component having the above-described configuration, the contained component may be a main component of a layer that forms the external electrode and is in contact with the ceramic body.

[0010] Furthermore, in the multilayer ceramic electronic component having the above configuration, the contained component may be a metal component contained in the dielectric layer.

[0011] In the multilayer ceramic electronic component having the above configuration, the surface layer portion may be provided within a range of 30% of the thickness of the protective portion from the surface of the protective portion toward the inside of the ceramic body.

[0012] In the multilayer ceramic electronic component having the above configuration, the amount of the oxide in the surface layer portion may be 10.0 times or more the amount of the contained component.

[0013] In the multilayer ceramic electronic component having the above configuration, the amount of the oxide in the surface layer portion may be 25 times or less the amount of the contained component.

[0014] In order to achieve the above object, a method for manufacturing a multilayer ceramic electronic component can include the steps of: preparing an unfired ceramic body including a precursor portion of a capacitance-forming portion formed by alternately stacking unfired first internal electrode layers and unfired second internal electrode layers, either of which contains as a component a metal having a melting point lower than 1100°C, with an unfired dielectric layer sandwiched therebetween; and a precursor portion of a protective portion provided around the precursor portion of the capacitance-forming portion; firing the unfired ceramic body to obtain a ceramic body; performing an oxidation treatment on a surface layer portion of the protective portion of the fired ceramic body; and forming an external electrode on the fired ceramic body.

[0015] In the method for manufacturing a monolithic ceramic electronic component having the above configuration, the step of performing the oxidation treatment may include a step of applying a pro-oxidant to the surface of the protective portion.

[0016] In the method for producing a monolithic ceramic electronic component having the above configuration, the pro-oxidant may include potassium permanganate.

[0017] In the method for manufacturing a multilayer ceramic electronic component having the above configuration, when the first internal electrode layer and the second internal electrode layer contain a copper component, the ceramic body may include a liquid phase containing Si element as a main component when unsintered.

[0018] In order to achieve the above object, another method for manufacturing a multilayer ceramic electronic component can include the steps of: preparing an unfired ceramic body including a precursor portion of a capacitance forming portion formed by alternately stacking unfired first internal electrode layers and unfired second internal electrode layers with unfired dielectric layers sandwiched therebetween; and a precursor portion of a protective portion provided around the precursor portion of the capacitance forming portion; firing the unfired ceramic body; performing an oxidation treatment on a surface layer portion of the protective portion of the fired ceramic body; and forming an external electrode containing, as a component, a metal having a melting point lower than 1100°C on the fired ceramic body.

[0019] In the method for manufacturing a monolithic ceramic electronic component having the above configuration, the step of performing the oxidation treatment may include a step of applying a pro-oxidant to the surface of the protective portion. [Effects of the Invention]

[0020] According to the present invention, it is possible to prevent leakage current from flowing between the external electrodes through the surface layer portion of the ceramic body. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a perspective view of a multilayer ceramic capacitor according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor taken along line AA′ in FIG. [Figure 3] FIG. 3 is a cross-sectional view of the multilayer ceramic capacitor taken along line BB' in FIG. [Figure 4] FIG. 4 is an enlarged cross-sectional view of a portion of the multilayer ceramic capacitor according to the embodiment. [Figure 5] 5A is a partially enlarged cross-sectional view of the multilayer ceramic capacitor according to the embodiment, and FIG. 5B is a partially enlarged cross-sectional view of a conventional multilayer ceramic capacitor. [Figure 6] FIG. 6 is a flowchart showing an example of a method for manufacturing the multilayer ceramic capacitor according to the embodiment. [Figure 7] 7(A) and 7(B) are diagrams illustrating the lamination process. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings show X-axis, Y-axis, and Z-axis, which are mutually orthogonal as appropriate. The X-axis, Y-axis, and Z-axis are common to all the drawings. The X-axis direction corresponds to the third direction, the Y-axis direction corresponds to the second direction, and the Z-axis direction corresponds to the first direction.

[0023] [Overall Configuration of Multilayer Ceramic Capacitor 10] 1 to 5 are diagrams showing an example of a multilayer ceramic capacitor 10 according to an embodiment of the present invention. FIG. 1 is a perspective view of the multilayer ceramic capacitor 10. FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor 10 taken along line AA' in FIG. 1. FIG. 3 is a cross-sectional view of the multilayer ceramic capacitor 10 taken along line BB' in FIG. 1. FIG. 4 is a partially enlarged cross-sectional view of the multilayer ceramic capacitor 10 according to an embodiment. FIG. 5(A) is a partially enlarged cross-sectional view of the multilayer ceramic capacitor 10 according to an embodiment. FIG. 5(B) is a partially enlarged cross-sectional view of a conventional multilayer ceramic capacitor 50.

[0024] The multilayer ceramic capacitor 10 includes a ceramic body 11 having a substantially rectangular parallelepiped shape. Of the six faces of the ceramic body 11, the opposing main faces are referred to as the upper and lower faces, and the remaining four faces are referred to as side faces. Generally, the main faces have the largest area. A first external electrode 14a and a second external electrode 14b are provided on the surface of the ceramic body 11, spaced apart from each other. In the example shown in FIGS. 1 to 3, the first external electrode 14a is provided on one of two opposing side faces (first side face and second side face), and the second external electrode 14b is provided on the other. The first external electrode 14a extends from the first side face to the four adjacent faces. The second external electrode 14b extends from the second side face to the four adjacent faces. However, the first external electrode 14a and the second external electrode 14b are spaced apart from each other.

[0025] As long as the first external electrode 14a and the second external electrode 14b are spaced apart, they can be provided at any position on the surface of the ceramic body 11. For example, the first external electrode 14a and the second external electrode 14b may be spaced apart on the same surface of the ceramic body 11, or the first external electrode 14a and the second external electrode 14b may be spaced apart on two adjacent surfaces or two opposing surfaces of the ceramic body 11.

[0026] As long as the first external electrode 14a and the second external electrode 14b are spaced apart from each other, they may extend from the surface of the ceramic body 11 on which they are provided to any other surface. For example, they may extend to an adjacent surface, or may extend further from the surface on which they are provided.

[0027] The multilayer ceramic component has a first direction, which is the stacking direction, a second direction perpendicular to the stacking direction and where two opposing surfaces intersect, and a third direction perpendicular to the first direction and perpendicular to the second direction and where two opposing surfaces intersect. The first, second, and third directions are orthogonal to each other. The stacking direction can be set in any of the length, width, and height directions of the ceramic body 11.

[0028] 1 to 3, the stacking direction, i.e., the first direction, is the Z-axis direction, which is the height direction of the ceramic body 11 and the direction in which the internal electrode layers face each other. In FIGS. 1 to 3, the second direction perpendicular to the stacking direction is the X-axis direction, which is the length direction of the ceramic body 11, the direction in which the first side surface and the second side surface of the ceramic body 11 face each other, and the direction in which the first external electrode 14a and the second external electrode 14b face each other. In FIGS. 1 to 3, the third direction perpendicular to the stacking direction (first direction) and the second direction is the Y-axis direction, which is the width direction of the internal electrode layers and the direction in which two side surfaces (third and fourth side surfaces) of the four side surfaces of the ceramic body 11 other than the first and second side surfaces face each other. The X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to one another.

[0029] The ceramic body 11 has a configuration in which dielectric layers 15 containing a ceramic material that functions as a dielectric and internal electrode layers are alternately stacked. The internal electrode layers include a plurality of first internal electrode layers 12 and a plurality of second internal electrode layers 13. The first internal electrode layers 12 and the second internal electrode layers 13 are alternately stacked. Edges of the first internal electrode layers 12 are extended to the surface of the ceramic body 11 on which the first external electrode 14a is provided. Edges of the second internal electrode layers 13 are extended to the surface of the ceramic body 11 on which the second external electrode 14b is provided. Note that it is sufficient that the first internal electrode layers 12 and the second internal electrode layers 13 are exposed in different regions on the surface of the laminate and are electrically connected to different external electrodes. The different regions on the surface of the laminate may be respective surface regions on opposing surfaces of the laminate, respective surface regions on adjacent surfaces of the laminate, or different surface regions on the same surface of the laminate. As long as the different external electrodes are spaced apart, the first internal electrode layers 12 and the second internal electrode layers 13 may extend from the surfaces exposed in the surface region of the laminate to other surfaces. In the example of Figures 1 to 3, the edge of the first internal electrode layer 12 is drawn to the first side surface of the ceramic body 11 on which the first external electrode 14a is provided. The edge of the second internal electrode layer 13 is drawn to the second side surface of the ceramic body 11 on which the second external electrode 14b is provided.

[0030] As a result, the first internal electrode layer 12 is electrically connected to the first external electrode 14a, and the second internal electrode layer 13 is electrically connected to the second external electrode 14b. As a result, the multilayer ceramic capacitor 10 has a configuration in which capacitor units are stacked, i.e., a capacitance forming portion 16. In addition, in a laminate of dielectric layers 15 and internal electrode layers, the internal electrode layers are arranged as the outermost layers in the stacking direction, and the upper and lower surfaces of the laminate are covered with a cover portion 18. The cover portion 18 is mainly composed of a ceramic material.

[0031] The size of the multilayer ceramic capacitor 10 may be, for example, 0.25 mm in length, 0.125 mm in width, and 0.125 mm in height, or 0.4 mm in length, 0.2 mm in width, and 0.2 mm in height, or 0.6 mm in length, 0.3 mm in width, and 0.3 mm in height, or 1.0 mm in length, 0.5 mm in width, and 0.5 mm in height, or 3.2 mm in length, 1.6 mm in width, and 1.6 mm in height, or 4.5 mm in length, 3.2 mm in width, and 2.5 mm in height, but is not limited to these sizes. The size of the multilayer ceramic capacitor 10 may be, for example, length > width ≥ height, width > length ≥ height, height > length ≥ width, or height > width ≥ length.

[0032] The ceramic body 11 has a capacitance-forming portion 16 and a protective portion 17. The protective portion 17 forms the periphery of the ceramic body 11.

[0033] The protective portion 17 includes a cover portion 18, a side margin portion 19, and an end margin portion 20. The cover portion 18 is located outside the capacitance forming portion 16 in the stacking direction, i.e., outside the capacitance forming portion 16 in the Z-axis direction in the example of FIGS. 1 to 3. The side margin portion 19 is provided outside the capacitance forming portion 16 in a direction perpendicular to the stacking direction. The side margin portion 19 is provided as a region that does not include the edge portions of the first internal electrode layers 12 and the second internal electrode layers 13 that are extended to the surface of the ceramic body 11 in the direction perpendicular to the stacking direction. That is, in the example of FIGS. 1 to 3, the side margin portion 19 is located outside the capacitance forming portion 16 in the Y-axis direction. The end margin portion 20 is provided outside the capacitance forming portion 16 in the direction perpendicular to the stacking direction. The end margin portions 20 are provided as regions including the edge portions of the first internal electrode layers 12 and the second internal electrode layers 13 that are drawn out to the surface of the ceramic body 11 in a direction perpendicular to the stacking direction. That is, the end margin portions 20 are located outside the capacitance forming portions 16 in the X-axis direction in the example of FIGS.

[0034] The side margins 19 are regions consisting only of the dielectric layers. The end margins 20 are regions including the dielectric layers and the edge portions of the first internal electrode layers 12 and the second internal electrode layers 13 that are drawn to the surface of the ceramic body 11.

[0035] The capacitance forming portion 16 is disposed inside the protective portion 17 and constitutes a functional portion. The capacitance forming portion 16 is formed by laminating a plurality of first internal electrode layers 12 and a plurality of second internal electrode layers 13 with dielectric layers 15 (see FIG. 2) interposed therebetween. In the example of FIGS. 1 to 3, they are laminated in the Z-axis direction. The internal electrode layers 12, 13 are both sheet-shaped extending along a plane perpendicular to the lamination direction and are alternately arranged in the lamination direction. In the example of FIGS. 1 to 3, they are sheet-shaped extending along the XY plane and are alternately arranged along the Z-axis direction.

[0036] The first internal electrode layers 12 and the second internal electrode layers 13 are mainly composed of base metals such as nickel (Ni), copper (Cu), tin (Sn), etc., or alloys containing these. Noble metals such as platinum (Pt), palladium (Pd), silver (Ag), gold (Au), etc., or alloys containing these may also be used as the main component of the first internal electrode layers 12 and the second internal electrode layers 13. The main component of the first internal electrode layers 12 and the second internal electrode layers 13 may be the same or different.

[0037] 2, the first internal electrode layer 12 is extended to, for example, one end face 11a of the ceramic body 11 and connected to one external electrode 14a. The second internal electrode layer 13 is extended to the other end face 11a and connected to the other external electrode 14b.

[0038] The dielectric layers 15 are made of dielectric ceramics. In the multilayer ceramic capacitor 10, a dielectric ceramic with a high dielectric constant is used to increase the capacitance of each dielectric layer 15 between the internal electrode layers 12 and 13. Examples of high dielectric constant dielectric ceramics include perovskite-structured materials containing barium (Ba) and titanium (Ti), such as barium titanate (BaTiO).

[0039] In addition to barium titanate-based materials, the dielectric ceramics may also be strontium titanate (SrTiO3)-based, calcium titanate (CaTiO3)-based, magnesium titanate (MgTiO3)-based, calcium zirconate (CaZrO3)-based, calcium titanate zirconate (Ca(Zr,Ti)O3)-based, barium zirconate (BaZrO3)-based, titanium oxide (TiO2)-based, etc.

[0040] The dielectric layer 15 may contain Si (silicon) element in addition to the above main components.

[0041] The dielectric layer 15 may also contain elemental copper.

[0042] The protective portion 17 is also made of a dielectric ceramic. In the protective portion 17, the cover portion 18 and the end margin portion 20 preferably have the same main component as the dielectric layer 15, from the viewpoint of suppressing internal stress, etc.

[0043] In the protective portion 17, the side margin portion 19 has the same main component as the dielectric layer 15 and can contain Si elements.

[0044] The external electrodes 14a, 14b each have a base film 21 formed to cover the lead portions of the internal electrode layers 12, 13 and part of the surface of the ceramic body, and a plating film 22 formed on the base film 21. The base film 21 is formed, for example, by baking a conductive paste or by sputtering. The plating film 22 is formed by electrolytic plating. Each film of the external electrodes 14a, 14b is formed of a metal or alloy containing, for example, nickel (Ni), copper (Cu), tin (Sn), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), or aluminum (Al) as a main component. The external electrodes 14a, 14b can also be formed by printing and drying a conductive paste containing a curable resin, such as resin Ag.

[0045] [Detailed configuration of protection unit 17] Here, the detailed configuration of the protective portion 17 will be described with reference to Figs. 4 to 5(B). Fig. 4 is a partially enlarged cross-sectional view of the multilayer ceramic capacitor 10 according to the embodiment. Fig. 4 shows an enlarged view of the upper left X1 and upper right X2 in Fig. 3. Fig. 5(A) is a partially enlarged cross-sectional view of the multilayer ceramic capacitor 10 according to the embodiment. Fig. 5(B) is a partially enlarged cross-sectional view of a conventional multilayer ceramic capacitor 50 containing copper (Cu) in the internal electrode layers. These figures show first metal-containing particles (particles mainly composed of CuO) 151 and second metal-containing particles (particles mainly composed of Cu) 152, but these are drawn schematically and do not accurately represent their actual dimensions or arrangement.

[0046] Among the first metal-containing particles 151, those not exposed on the surface of protective section 17 are mostly composed of CuO, while those exposed on the surface of protective section 17 are CuO particles in which some or all of the surface is covered with CuO, and these are collectively referred to in this specification as first metal-containing particles 151. According to the present invention, Cu particles become particles primarily composed of CuO when thermally oxidized, and the Cu particles exposed on the surface of protective section 17 become particles primarily composed of CuO because their surface portions are converted to CuO by the influence of moisture in the air, etc. First metal-containing particles 151 are defined as particles containing CuO as the primary component.

[0047] Of the second metal-containing particles 152, those not exposed on the surface of the protective portion 17 are mostly composed of Cu, but in the particles exposed on the surface of the protective portion 17, only the Cu on the particle surface may be oxidized. The oxidized Cu portion on the particle surface exposed on the surface of the protective portion 17 is not oxidized by heat but is oxidized by the influence of moisture in the air, and therefore the oxidized form is not CuO but mostly CuO. The second metal-containing particles 152 referred to in this specification are particles whose main component is Cu and whose surface exposed from the protective portion 17 is mostly oxidized to CuO. When a particle whose main component is Cu is not exposed from the protective portion 17, there are no oxidized portions such as CuO on the surface of the particle whose main component is Cu.

[0048] The first metal-containing particles 151 and the second metal-containing particles 152 may be present not only on both the surface and inside of the protective section 17 as shown in the figures, but also only on the surface of the protective section 17, or only inside and not on the surface. While only the first metal-containing particles 151 are shown in Figures 4 and 5(A), it is also possible for the first metal-containing particles 151 to be present primarily, with a small amount of the second metal-containing particles 152 present. The number, proportion, and arrangement of these particles do not have to be as shown in the figures.

[0049] 4, a cover portion 18 is formed between the main surface 11c and the uppermost first internal electrode layer 12. First metal-containing particles 151 containing, as a main component, CuO, which is an oxide of Cu, a component contained in the internal electrode layers 12 and 13, are arranged in a surface layer portion 181 including the main surface 11c of the cover portion 18. Although not shown in an enlarged view, a cover portion 18 is also formed between the main surface 11c and the lowermost second internal electrode layer 13, and first metal-containing particles 151 are arranged in the surface layer portion 181.

[0050] A side margin portion 19 is formed between the side surface 11b and the internal electrode layers 12, 13. In a surface layer portion 191 including the side surface 11b of the side margin portion 19, first metal-containing particles 151 are arranged, similar to the surface layer portion 181 of the cover portion 18, which are contained in the internal electrode layers 12, 13 and contain, as a main component, CuO, which is an oxide of Cu, the main component.

[0051] The thickness of the cover portion 18 is t

[18] . The thickness of the surface layer portion 181 of the cover portion 18 is t

[0181] . The thickness t

[0181] of the surface layer portion 181 may be set within a range of 30% of the thickness t

[18] of the cover portion 18. The presence of the first metal-containing particles in the surface layer portion of the dielectric layer can improve the mechanical strength, such as the flexural strength, of the multilayer ceramic component.

[0052] The thickness of the side margin portion 19 is t

[19] . The thickness of the surface layer portion 191 in the side margin portion 19 is t

[0191] . The thickness t

[0191] of the surface layer portion 191 is set within a range of 30% of the thickness t

[19] of the side margin portion 19. The presence of the first metal-containing particles in the surface layer portion of the dielectric layer can improve the mechanical strength, such as the flexural strength, of the multilayer ceramic component.

[0053] In this way, by disposing first metal-containing particles 151 in surface layer portion 181 of cover portion 18 and surface layer portion 191 of side margin portion 19, it is possible to suppress the leakage current flowing through protective portion 17. In surface layer portion 181 of cover portion 18 and surface layer portion 191 of side margin portion 19, the amount of first metal-containing particles 151 is desirably 10.0 to 25 times the amount of Cu, which is a contained component in cover portion 18 and side margin portion 19. This makes it possible to effectively suppress the leakage current flowing through protective portion 17.

[0054] 5(B) shows a conventional multilayer ceramic capacitor 50 containing Cu in at least one of the internal electrode layers 12, 13 and the external electrodes 14a, 14b. Second metal-containing particles 152 are disposed in the cover portion 18 of the conventional multilayer ceramic capacitor 50. This is thought to be because, when the internal electrode layers 12, 13 contain Cu, the Cu contained in the internal electrode layers 12, 13 is transported to the vicinity of the surfaces of the cover portion 18 and the side margin portion 19 during the sintering process of the ceramic body 11. In particular, when the main component of the internal electrode layers 12, 13 is Cu, the phenomenon of Cu being transported to the vicinity of the surface of the protective portion 17 is likely to occur via Si elements added to the dielectric material to promote low-temperature sintering.

[0055] Furthermore, if the external electrodes 14a, 14b contain Cu, and the electrodes 14a, 14b are provided before sintering, this is thought to be because the Cu contained in the external electrodes 14a, 14b is transported to the vicinity of the surfaces of the cover portion 18 and the side margin portion 19 during the sintering process in which the ceramic body 11 and the external electrodes 14a, 14b are sintered simultaneously.If the external electrodes 14a, 14b are provided after sintering, this is thought to be because the Cu contained in the external electrodes 14a, 14b is transported to the vicinity of the surfaces of the cover portion 18 and the side margin portion 19 during the baking process of the external electrodes 14a, 14b.

[0056] Second metal-containing particles 152 are conductive. Therefore, when second metal-containing particles 152 are present on or near the surface of cover portion 18 or side margin portion 19, current tends to flow through second metal-containing particles 152. In other words, leakage current tends to increase.

[0057] In contrast, as shown in Fig. 5(A), first metal-containing particles 151 containing copper oxide particles, primarily CuO, are disposed in the cover portion 18 of the multilayer ceramic capacitor 10 of this embodiment. Current flows less easily through the first metal-containing particles 151 than through the second metal-containing particles 152. This makes it possible to suppress an increase in leakage current in the multilayer ceramic capacitor 10. Although Fig. 5(A) shows the cover portion 18, the first metal-containing particles 151 are also disposed in the side margin portions 19, so an increase in leakage current in the side margin portions 19 is also suppressed.

[0058] In this embodiment, Cu is used as a component of the internal electrode layers 12, 13 or the external electrodes 14a, 14b. Therefore, first metal-containing particles 151, primarily composed of CuO, are disposed as particles that suppress leakage current. In other words, in this embodiment, if components forming the internal electrode layers 12, 13 or the external electrodes 14a, 14b are transported by heat to the surface layer of the ceramic body 11, the generation of leakage current is suppressed by providing an oxide of the component. Therefore, the type of oxide is determined depending on the components contained in the internal electrode layers 12, 13 or the external electrodes 14a, 14b. In this embodiment, Cu is described as one of the metals having a melting point below 1100°C, which is the firing temperature of the dielectric. If the internal electrode layers 12, 13 or the external electrodes 14a, 14b contain a metal other than Cu whose melting point is below 1100°C, the generation of leakage current is suppressed by the oxide of that metal. If the dielectric layer 15 contains a metal whose melting point is lower than 1100° C. as a component, the oxide of such a component also suppresses the occurrence of leakage current.

[0059] [Manufacturing method for multilayer ceramic capacitors] Fig. 6 is a flowchart illustrating a method for manufacturing the multilayer ceramic capacitor 10. Fig. 7(A) and Fig. 7(B) are diagrams illustrating the lamination step.

[0060] (Step S01: Raw material powder preparation process) First, a dielectric material for forming the dielectric layer 15 is prepared. The A-site elements and B-site elements contained in the dielectric layer 15 are typically present in the form of a sintered compact of ABO3 particles. For example, BaTiO3 is a tetragonal compound with a perovskite structure and exhibits a high dielectric constant. BaTiO3 can generally be obtained by synthesizing barium titanate by reacting a titanium source such as titanium dioxide with a barium source such as barium carbonate. Various methods are known for synthesizing the ceramic that is the main component of the dielectric layer 15, including the solid-phase method, the sol-gel method, and the hydrothermal method. Any of these methods can be used in this embodiment.

[0061] The resulting ceramic powder is then doped with a predetermined additive compound depending on the purpose, such as oxides of magnesium (Mg), manganese (Mn), vanadium (V), chromium (Cr), rare earth elements (yttrium (Y), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb)), oxides containing cobalt (Co), nickel, lithium (Li), boron (B), sodium (Na), potassium (K), or silicon (Si), or glasses containing cobalt, nickel, lithium, boron, sodium, potassium, or silicon.

[0062] For example, a ceramic material is prepared by wet-mixing a ceramic raw material powder with a compound containing an additive compound, followed by drying and pulverization. For example, the ceramic material obtained as described above may be pulverized as necessary to adjust the particle size, or may be combined with a classification process to adjust the particle size. A dielectric material is obtained by the above process.

[0063] (Step S02: Lamination process) Next, a binder such as polyvinyl butyral (PVB) resin, an organic solvent such as ethanol or toluene, and a plasticizer are added to the obtained dielectric material and wet mixed. Using the obtained slurry, a dielectric green sheet 52 having a thickness of, for example, 0.5 μm to 1.0 μm is coated on a substrate 51 by, for example, a die coater method or a doctor blade method, and then dried. The substrate 51 is, for example, a PET (polyethylene terephthalate) film.

[0064] Next, as illustrated in Fig. 7(A), an internal electrode pattern 53 is formed on a dielectric green sheet 52. In Fig. 7(A), as an example, four layers of internal electrode patterns 53 are formed on the dielectric green sheet 52 at predetermined intervals. The formation method is not particularly limited, but for example, an electrode paste containing Ni as a main component may be used, or a paste containing Ni as a main component may be mixed with a component containing Cu. Vacuum film formation such as sputtering using a Ni-Cu alloy target, or simultaneous sputtering using individual Ni and Cu targets may also be used. The dielectric green sheet 52 on which the internal electrode patterns 53 are formed is defined as a lamination unit.

[0065] Next, while peeling off the dielectric green sheet 52 from the substrate 51, the lamination units are laminated as shown in FIG. 7(B).

[0066] Next, a predetermined number of cover sheets (e.g., 2 to 10 layers) are laminated on top and bottom of the laminate obtained by stacking the laminate units, and are thermocompression bonded, and then cut to the predetermined chip dimensions (e.g., 1.0 mm x 0.5 mm). In the example of Figure 7(B), cutting is performed along the dotted lines. The cover sheets may have the same components as the dielectric green sheets 52, or may contain different additive compounds. This forms a precursor portion of the capacitance-forming portion 16, and an unfired ceramic element is formed around it, with the precursor portion of the protective portion 17 formed therearound.

[0067] (Step S03: Firing) In step S03, the green ceramic body obtained in step S02 is fired to produce the ceramic body 11 of the multilayer ceramic capacitor 10 shown in Fig. 1. The firing temperature in step S03 can be determined based on the sintering temperature of the ceramic body. Furthermore, firing can be performed, for example, in a reducing atmosphere or a low-oxygen partial pressure atmosphere.

[0068] By firing the green ceramic body, the Cu elements in the green internal electrode layers move toward the surface of the ceramic body, using the Si elements contained in the ceramic body as a medium.

[0069] (Step S04: Oxidation treatment) In step S04, Cu elements that have migrated toward the surface of the unsintered ceramic body during the firing process are oxidized to form copper oxide. The oxidation treatment involves another heat treatment in a weakly oxidizing atmosphere, thereby disposing first metal-containing particles 151 in surface layer portion 181 of cover portion 18 and surface layer portion 191 of side margin portion 19. Here, the weakly oxidizing atmosphere refers to a state in which 60 ppm or less of oxygen is mixed in an inert gas such as nitrogen.

[0070] The temperature and treatment time for the oxidation treatment can be set as appropriate. For example, the temperature can be set to 300°C or higher and 600°C or lower, and the treatment time can be set as appropriate from 30 seconds to 30 minutes. Note that these temperature and treatment time can be set as appropriate within the above ranges even in the case of materials other than Cu.

[0071] Prior to the oxidation treatment, potassium permanganate may be applied to the surface of the ceramic body as an oxidation promoter.

[0072] (Step S05: Forming the base film) In step S05, a conductive base film 21 is formed on the end face 11a, the side face 11b, and the main face 11c shown in FIGS.

[0073] The base film 21 is formed by applying unfired electrode material to the end surface 11a, the side surface 11b, and the main surface 11c. The application method is, for example, a dipping method, but other conventionally known methods such as printing and sputtering, or a combination of these, may also be used. The unfired electrode material is then baked. The baking can be performed, for example, in a reducing atmosphere or a low-oxygen partial pressure atmosphere.

[0074] In this embodiment, a process can be performed to prevent oxidation of the external electrodes 14a, 14b. Specifically, before baking, the electrode material is subjected to a rust prevention process, such as by applying a rust inhibitor such as phosphate or silicate to the electrode material. This can prevent oxidation of the external electrodes 14a, 14b.

[0075] The external electrodes 14a, 14b may be formed in a different order from the flowchart illustrated in FIG. 6. For example, the external electrodes 14a, 14b may be formed by providing an unfired electrode material after the process of step S02 in FIG. 6. In this case, the unfired electrode material is subjected to rust prevention treatment, for example, by applying an anti-rust agent such as phosphate or silicate to the unfired electrode material. Then, in the firing process of step S03, the electrode material is fired together with the ceramic body to form the external electrodes 14a, 14b. This prevents oxidation of the external electrodes 14a, 14b. In step S04, which is executed after step S03, an oxidation treatment is performed, but oxidation of the external electrodes 14a, 14b is prevented.

[0076] (Step S06: Plating film formation) In step S06, electrolytic plating is performed by immersing the ceramic body on which base film 21 has been formed in a plating solution for forming plating film 22. In this way, plating film 22 is formed.

[0077] In this manner, the multilayer ceramic capacitor 10 shown in FIGS. 1 to 3 is manufactured.

[0078] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in the description of this embodiment, the lamination direction of the dielectric layers 15 and the internal electrode layers 12, 13 is the Z direction of the multilayer ceramic capacitor 10, but it may be another direction such as the X direction or the Y direction. [Example]

[0079] Next, the values of leakage current in the multilayer ceramic capacitors of the examples will be explained together with the values of leakage current in the comparative examples.

[0080] The examples correspond to the multilayer ceramic capacitor 10 of the embodiment. Three types of examples, Example 1 to Example 3, were prepared by varying the combination of temperature and time of the oxidation treatment. Three types of comparative examples, Comparative Example 1 to Comparative Example 3, were also prepared by varying the combination of temperature and time of the oxidation treatment, and including an example in which no oxidation treatment was performed. The dimensions of the examples and comparative examples are length x width x height = 0.6 mm x 0.3 mm x 0.3 mm.

[0081] [Table 1]

[0082] Example 1 In Example 1, oxidation treatment was performed at 600°C for 30 seconds. As a result, the amount of Cu2O, which is an oxide, was 20.5 times the amount of Cu, which is the main component of the internal electrode layers 12 and 13. The amounts of Cu2O and Cu were obtained by analyzing the surface of the ceramic body 11 using X-ray photoelectron spectroscopy (XPS). Specifically, the peaks of the Cu2p spectrum were separated using XPS, and the amounts of Cu2O and Cu were calculated based on the areas of each peak. This calculation method was also used in the other Examples and Comparative Examples. The DC resistance in Example 1 was 5.87 GΩ.

[0083] Example 2 In Example 2, oxidation treatment was performed at 400° C. for 10 minutes. As a result, the amount of Cu2O, which is an oxide, was 18.2 times the amount of Cu, which is the main component of the internal electrode layers 12 and 13. The DC resistance in Example 2 was 4.26 GΩ.

[0084] Example 3 In Example 3, oxidation treatment was performed at 300° C. for 30 minutes. As a result, the amount of Cu2O, which is an oxide, was 10.9 times the amount of Cu, which is the main component of the internal electrode layers 12 and 13. The DC resistance in Example 3 was 1.91 GΩ.

[0085] (Comparative Example 1) No oxidation treatment was performed in Comparative Example 1. As a result, the amount of Cu2O, which is an oxide, was 0.2 times the amount of Cu, which is the main component of the internal electrode layers 12 and 13. The DC resistance in Comparative Example 1 was 0.02 GΩ.

[0086] (Comparative Example 2) In Comparative Example 2, oxidation treatment was performed at 200° C. for 30 minutes. As a result, the amount of Cu2O, which is an oxide, was 0.7 times the amount of Cu, which is the main component of the internal electrode layers 12 and 13. The DC resistance in Comparative Example 2 was 0.08 GΩ.

[0087] (Comparative Example 3) In Comparative Example 3, oxidation treatment was performed at 400°C for 45 minutes. As a result, the amount of Cu2O, which is an oxide, was 8.1 times the amount of Cu, which is the main component of the internal electrode layers 12 and 13. The DC resistance in Comparative Example 3 was 0.67 GΩ. By performing treatment for a time longer than 30 minutes, the amount of Cu newly diffused from the internal electrode layers 12 and 13 exceeded the amount that was oxidized.

[0088] Comparative Example 4 In Comparative Example 4, oxidation treatment was performed at 700°C for 1 minute. As a result, the amount of Cu2O, which is an oxide, was 1.7 times the amount of Cu, which is the main component of the internal electrode layers 12 and 13. The DC resistance in Comparative Example 3 was 0.23 GΩ. Because the treatment was performed at a temperature higher than 600°C, the amount of Cu newly diffused from the internal electrode layers 12 and 13 exceeded the amount that was oxidized.

[0089] In this way, by performing an appropriate oxidation treatment and increasing the amount of Cu2O, which is an oxide, it is possible to suppress the occurrence of leakage current. From the results of these examples and comparative examples, it was confirmed that by setting the amount of Cu2O to be 10.0 times or more and 25 times or less that of Cu, it is possible to effectively suppress the leakage current flowing through the protective portion 17.

[0090] In the above embodiment, the multilayer ceramic capacitor 10 has been described as an example of a multilayer ceramic electronic component, but the present invention is applicable to all multilayer ceramic electronic components in which dielectric layers and internal electrodes are stacked. Examples of such multilayer ceramic electronic components include chip varistors, chip thermistors, and multilayer inductors. [Explanation of symbols]

[0091] 10...Multilayer ceramic capacitor 11...Ceramic body 12,13...Internal electrode layer 14a,14b...External electrode 21...Base film 22...Plating film 151...first metal-containing particles

Claims

1. a ceramic body including a capacitance forming portion formed by alternately stacking first internal electrode layers and second internal electrode layers with dielectric layers sandwiched therebetween, and a protective portion provided around the capacitance forming portion; external electrodes formed on the surface of the ceramic body so as to be spaced apart from each other, the first internal electrode layer and the second internal electrode layer being led out, respectively; At least one of the dielectric layer, the first internal electrode layer, the second internal electrode layer, and the external electrode contains a metal having a melting point lower than 1100°C, an oxide of the contained component in the form of particles provided on a surface layer portion of the ceramic body between the pair of external electrodes; Multilayer ceramic electronic components.

2. The contained component is copper, and the particulate oxide is a copper oxide containing cuprous oxide as a main component. The multilayer ceramic electronic component according to claim 1 .

3. The contained component is a main component of at least one of the first internal electrode layers and the second internal electrode layers. The multilayer ceramic electronic component according to claim 1 .

4. the contained component is a main component of a layer that forms the external electrode and is in contact with the ceramic body; The multilayer ceramic electronic component according to claim 1 .

5. The contained component is a metal component contained in the dielectric layer. The multilayer ceramic electronic component according to claim 1 .

6. the surface layer portion is provided within a range of 30% of the thickness of the protective portion from the surface of the protective portion toward the inside of the ceramic body. The multilayer ceramic electronic component according to claim 1 .

7. The amount of the oxide in the surface layer portion is 10.0 times or more the amount of the contained component. The multilayer ceramic electronic component according to claim 1 .

8. The amount of the oxide in the surface layer portion is 25 times or less the amount of the contained component. The multilayer ceramic electronic component according to claim 5 .

9. a step of manufacturing an unfired ceramic body including: a precursor portion of a capacitance forming portion formed by alternately stacking unfired first internal electrode layers and unfired second internal electrode layers, either of which contains a metal having a melting point lower than 1100°C as a component, with a dielectric layer sandwiched therebetween; and a precursor portion of a protective portion provided around the precursor portion of the capacitance forming portion; a step of firing the green ceramic body to obtain a ceramic body; performing an oxidation treatment on a surface layer of the protective portion of the fired ceramic body; forming external electrodes on the fired ceramic body; A method for manufacturing a multilayer ceramic electronic component comprising:

10. The step of performing the oxidation treatment includes a step of applying an oxidation promoter to the surface of the protective part. The method for producing a multilayer ceramic electronic component according to claim 9.

11. The pro-oxidant includes potassium permanganate. The method for producing a multilayer ceramic electronic component according to claim 10.

12. When the first internal electrode layers and the second internal electrode layers contain a copper component, the ceramic body contains a liquid phase containing Si element as a main component when not fired. The method for producing a multilayer ceramic electronic component according to claim 9.

13. a step of manufacturing an unfired ceramic body including: a precursor portion of a capacitance forming portion formed by alternately stacking unfired first internal electrode layers and unfired second internal electrode layers with unfired dielectric layers sandwiched therebetween; and a precursor portion of a protective portion provided around the precursor portion of the capacitance forming portion; firing the green ceramic body; performing an oxidation treatment on a surface layer of the protective portion of the fired ceramic body; forming external electrodes containing a metal having a melting point below 1100°C as a component on the fired ceramic body; A method for manufacturing a multilayer ceramic electronic component comprising:

14. The step of performing the oxidation treatment includes a step of applying an oxidation promoter to the surface of the protective part. The method for producing a multilayer ceramic electronic component according to claim 13.

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