Multilayer ceramic capacitor and method for manufacturing a multilayer ceramic capacitor

Abstract

The present invention provides a laminated ceramic capacitor in which a surface protection layer, which is provided with high strength, is formed on an outer surface of a ceramic element. The laminated ceramic capacitor comprises: a ceramic element including a first internal electrode, a second internal electrode, and ceramic layers made from ceramic and laminated in a height direction, the ceramic layers having first main surfaces and second main surfaces facing the height direction, first side surfaces and second side surfaces facing in the width direction orthogonal to the height direction, and first end surfaces and second end surfaces facing in the length direction orthogonal to the height direction and the width direction; and a first external electrode formed on one end of the ceramic element and a second external electrode formed on the other end of the ceramic element, the first internal electrode being led out to the first end surface and electrically connected to the first external electrode, and the second internal electrode being led out to the second end surface and electrically connected to the second external electrode. The ceramic element comprises: a capacitance forming unit that contributes to the formation of capacitance and that has the first internal electrode and the second internal electrode disposed facing each other across the ceramic layers, the capacitance forming unit forming a rectangular parallelepiped shape having six faces; a non-capacitance forming unit that does not contribute to the formation of capacitance, the non-capacitance forming unit formed on outside of each of six faces of the capacitance forming unit that does not have the first internal electrode and the second internal electrode disposed facing each other across the ceramic layers; and a surface protection layer formed on at least a part of the outside of the non-capacitance forming unit and exposed at least on the first main surface, the second main surface, the first side surface, and the second side surface, the surface protection layer constituted by a ceramic that has a composition different from the ceramic constituting the non-capacitance forming unit.

Description

Technical Field

[0001] The present invention relates to a multilayer ceramic capacitor.

[0002] The present invention also relates to a method for manufacturing a multilayer ceramic capacitor suitable for manufacturing the multilayer ceramic capacitor of the present invention.

Background Art

[0003] Multilayer ceramic capacitors are widely used in electronic devices, electrical devices, and the like.

[0004] A conventional general multilayer ceramic capacitor includes a ceramic body in which a ceramic layer, a first internal electrode, and a second internal electrode are laminated in the height direction. The ceramic body includes a first main surface and a second main surface facing each other in the height direction, a first side surface and a second side surface facing each other in the width direction, and a first end surface and a second end surface corresponding to the length direction. In the ceramic body, the first internal electrode is led out to the first end surface, and the second internal electrode is led out to the second end surface. A first external electrode electrically connected to the first internal electrode is formed at one end of the ceramic body, and a second external electrode electrically connected to the second internal electrode is formed at the other end of the ceramic body.

[0005] The ceramic body includes a capacitance-forming section that contributes to capacitance formation, in which a first internal electrode and a second internal electrode are arranged facing each other with a ceramic layer in between. The ceramic body includes a protective layer between the capacitance-forming section and the first and second main surfaces, which is formed only of the ceramic layer and does not contain the first and second internal electrodes. The ceramic body also includes a side gap between the capacitance-forming section and the first and second side surfaces, which is formed only of the ceramic layer and does not contain the first and second internal electrodes. The side gap is provided so that the first and second internal electrodes are not exposed to the first and second side surfaces. Furthermore, the ceramic body includes a lead-out section between the capacitance-forming section and the first end surface, which is formed only of the first internal electrode and the ceramic layer and does not contain the second internal electrode, and a lead-out section between the capacitance-forming section and the second end surface, which is formed only of the second internal electrode and the ceramic layer and does not contain the first internal electrode. In this application, the protective layer, side gap, and lead-out section may be referred to as the non-capacitance-forming section.

[0006] In conventional multilayer ceramic capacitors, the same ceramic composition is often used for both the capacitance-forming ceramic and the non-capacitance-forming ceramic (protective layer, side gap, lead-out section). Specifically, for example, a ceramic green sheet with a conductive paste for the first internal electrode applied in a desired pattern shape, a ceramic green sheet with a conductive paste for the second internal electrode applied in a desired pattern shape, and a ceramic green sheet without conductive paste are prepared, stacked in a predetermined order, and fired to produce a ceramic body. In this case, if there is only one type of ceramic green sheet and all ceramic green sheets are of the same type, the capacitance-forming and non-capacitance-forming ceramics are composed of ceramics of the same composition.

[0007] When using the same type (one type) of ceramic green sheet for all components, the firing process of the ceramic substrate typically aims to improve the quality of the ceramic in the capacitance-forming section. Therefore, a firing profile, including firing temperature and time, is determined that is suitable for the ceramic in the capacitance-forming section. This is because the quality of the ceramic in the capacitance-forming section significantly affects the electrical characteristics, such as the capacitance, of the multilayer ceramic capacitor. However, since the structure of the capacitance-forming section and the non-capacitance-forming section differs (due to the presence or absence of internal electrodes, etc.), the optimal firing profile often differs between them.

[0008] As a result, even if the ceramic in the volume-forming section is formed to a good quality with an appropriate particle size, the ceramic in the non-volume-forming section (especially the protective layer and side gap) may end up with a lower quality, such as having an excessively large particle size.

[0009] Furthermore, if the ceramic in the non-capacitance-forming area is overfired and the particle size becomes too large, it may lead to a decrease in the strength of the first main surface, second main surface, first side surface, and second side surface of the ceramic body. However, the first and second end surfaces of the ceramic body are protected by the first and second external electrodes, so the problem of strength reduction is smaller compared to the first main surface, second main surface, first side surface, and second side surface.

[0010] A decrease in the strength of the outer surface of the ceramic element constitutes a serious defect in the quality of a multilayer ceramic capacitor. This is because external forces applied to the ceramic element can cause cracks or chips to form. When cracks or chips occur in the ceramic element, moisture can penetrate into the interior of the ceramic element, potentially causing the multilayer ceramic capacitor to fail.

[0011] Therefore, attempts have been made to improve the strength of the outer surface of the ceramic element in multilayer ceramic capacitors.

[0012] For example, in the multilayer ceramic capacitor (multilayer electronic component) described in Patent Document 1 (Japanese Patent Application Publication No. 2011-035145), the strength of the outer surface of the ceramic body is improved by using two different ceramic compositions for each part of a single ceramic body. Specifically, for example, in the multilayer ceramic capacitor disclosed in Figure 6 of Patent Document 1, a ceramic with a composition that exhibits a good dielectric constant is used for the capacitance-forming portion between the first internal electrode and the second internal electrode, while a ceramic with high strength is used for the non-capacitance-forming portion on the outer surface of the ceramic body, thereby improving the strength of the outer surface of the ceramic body.

[0013] In the multilayer ceramic capacitor described in Patent Document 2 (Japanese Patent Publication No. 2012-004236), one ceramic body is made using one type of ceramic green sheet. However, a water-soluble binder resin is added to the ceramic green sheet in advance, and before the firing process, the outer surface of the unfired ceramic body is brought into contact with water or the like to dissolve specific elements from the outer surface of the unfired ceramic body. This makes the ceramic composition of the outer surface of the ceramic body after firing different from the ceramic composition of the capacitance-forming part of the ceramic body. As a result, the ceramic composition of the outer surface of the ceramic body after firing is made to have high strength.

[0014] In the multilayer ceramic capacitor described in Patent Document 3 (Japanese Patent Publication No. 2007-266223), ceramics with different compositions are used for the ceramic green sheet that forms the capacitance-forming portion and the side gap, and for the ceramic green sheet of the protective layer that is laminated above and below it. Specifically, the ceramic green sheet of the capacitance-forming portion and the side gap uses a ceramic with a composition suitable for exhibiting a good dielectric constant, while the ceramic green sheet of the protective layer uses a ceramic that exhibits high strength. [Prior art documents] [Patent Documents]

[0015] [Patent Document 1] Japanese Patent Publication No. 2011-035145 [Patent Document 2] Japanese Patent Publication No. 2012-004236 [Patent Document 3] Japanese Patent Publication No. 2007-266223 [Overview of the Initiative] [Problems that the invention aims to solve]

[0016] The multilayer ceramic capacitor described in Patent Document 1 has a complicated manufacturing process because it uses two different ceramic compositions for each part of a single ceramic body. In particular, using ceramics of different compositions for the capacitance formation part and the side gap requires an extremely complex and difficult manufacturing process. The multilayer ceramic capacitor described in Patent Document 1 had the problem of low productivity.

[0017] The multilayer ceramic capacitor described in Patent Document 2 also had the problem of low productivity. Specifically, it required a complex process in which a water-soluble binder resin had to be added to the ceramic green sheet in advance, and then the outer surface of the unfired ceramic body had to be brought into contact with water or the like before the firing process of the ceramic body to dissolve specific elements from the outer surface of the unfired ceramic body. Furthermore, the process of bringing the outer surface of the unfired ceramic body into contact with water or the like to dissolve specific elements is difficult to control, and if the control is not properly performed, there was a risk that variations in the strength of the outer surface of the ceramic body or variations in electrical characteristics such as capacitance would occur among the manufactured units.

[0018] The multilayer ceramic capacitor described in Patent Document 3 has the problem that while the strength of the first and second main surfaces of the ceramic body where the protective layer is exposed on the outer surface is improved, the strength of the first and second side surfaces of the ceramic body where the side gap is exposed on the outer surface is not improved. In other words, since the ceramic constituting the side gap has the same composition as the ceramic constituting the capacitance forming part, there was a risk that the strength of the first and second side surfaces of the ceramic body would remain low. [Means for solving the problem]

[0019] The present invention has been made to solve the above-mentioned conventional problems, and as a means, a multilayer ceramic capacitor according to one embodiment of the present invention is made of ceramic and comprises a ceramic body including a ceramic layer, a first internal electrode and a second internal electrode, which are stacked in the height direction and have a first main surface and a second main surface facing each other in the height direction, a first side surface and a second side surface facing each other in the width direction perpendicular to the height direction and a first end surface and a second end surface facing each other in the length direction perpendicular to the height direction and width direction, a first external electrode formed at one end of the ceramic body and a second external electrode formed at the other end of the ceramic body, wherein the first internal electrode is led out to the first end surface and electrically connected to the first external electrode and the second internal electrode A multilayer ceramic capacitor in which the electrodes are drawn out to a second end face and electrically connected to a second external electrode, wherein the ceramic body has a rectangular parallelepiped shape with six faces, in which the first internal electrode and the second internal electrode are arranged facing each other via a ceramic layer, and comprises a capacitance forming portion that contributes to the formation of capacitance; a non-capacitance forming portion formed on the outside of each of the six faces of the capacitance forming portion, in which the first internal electrode and the second internal electrode are not arranged facing each other via a ceramic layer and do not contribute to the formation of capacitance; and a surface protection layer formed on at least a portion of the outside of the non-capacitance forming portion and exposed on at least the first main face, the second main face, the first side, and the second side, and made of a ceramic with a different composition from the ceramic constituting the non-capacitance forming portion.

[0020] Furthermore, a method for manufacturing a multilayer ceramic capacitor according to one embodiment of the present invention includes the steps of: preparing an unfired ceramic body having a first main surface and a second main surface facing each other in the height direction, a first side surface and a second side surface facing each other in the width direction perpendicular to the height direction, and a first end surface and a second end surface facing each other in the length direction perpendicular to the height direction and width direction, and stacked in the height direction, and including a ceramic green sheet, a conductive paste layer for a first internal electrode, and a conductive paste layer for a second internal electrode; attaching elemental powder and / or ceramic powder to at least the first main surface, the second main surface, the first side surface, and the second side surface of the unfired ceramic body; firing the unfired ceramic body with the attached powder to produce a ceramic body including a ceramic layer stacked in the height direction, a first internal electrode, and a second internal electrode; and The invention comprises the steps of forming a first external electrode electrically connected to a first internal electrode at one end of a ceramic body, and forming a second external electrode electrically connected to a second internal electrode at the other end of the ceramic body, wherein the manufactured ceramic body has a capacitance-forming portion that contributes to capacitance formation, having a rectangular parallelepiped shape with six faces, in which the first internal electrode and the second internal electrode are arranged facing each other via a ceramic layer; a non-capacitance-forming portion that does not contribute to capacitance formation, formed on the outside of each of the six faces of the capacitance-forming portion, in which the first internal electrode and the second internal electrode are not arranged facing each other via a ceramic layer; and a surface protection layer formed on at least a portion of the outside of the non-capacitance-forming portion and exposed on at least the first main surface, second main surface, first side surface, and second side surface, and made of a ceramic with a different composition from the ceramic constituting the non-capacitance-forming portion. [Effects of the Invention]

[0021] In one embodiment of the present invention, a multilayer ceramic capacitor has a surface protective layer formed on the first main surface, second main surface, first side surface, and second side surface of the ceramic body. Therefore, even if an external force is applied to the ceramic body, the occurrence of cracks or chips in the ceramic body is suppressed.

[0022] According to the method for manufacturing a multilayer ceramic capacitor according to an embodiment of the present invention, a multilayer ceramic capacitor according to an embodiment of the present invention can be manufactured easily and with high productivity.

Brief Description of the Drawings

[0023] [Figure 1] It is a perspective view of the multilayer ceramic capacitor 100. [Figure 2] It is a cross-sectional view of the multilayer ceramic capacitor 100. [Figure 3] It is a cross-sectional view of the multilayer ceramic capacitor 100. [Figure 4] It is a cross-sectional view of the multilayer ceramic capacitor 200.

Embodiments for Carrying Out the Invention

[0024] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[0025] Each embodiment exemplarily shows an embodiment of the present invention, and the present invention is not limited to the content of the embodiment. Also, it is possible to combine the contents described in different embodiments and implement them, and the implementation content in that case is also included in the present invention. Further, the drawings are for assisting in understanding the specification and may be drawn schematically, and the ratio of the drawn components or the dimensions between the components may not match the ratio of those dimensions described in the specification. Also, there are cases where the components described in the specification are omitted in the drawings or the number is omitted in the drawing.

[0026] [First Embodiment] Figures 1 to 3 show a multilayer ceramic capacitor 100 according to the first embodiment. However, Figure 1 is a perspective view of the multilayer ceramic capacitor 100. Figure 2 is a cross-sectional view of the multilayer ceramic capacitor 100, showing the II-II section indicated by the dashed-dotted arrow in Figure 1. Figure 3 is also a cross-sectional view of the multilayer ceramic capacitor 100, showing the III-III section indicated by the dashed-dotted arrow in Figure 1. The height direction T, width direction W, and length direction L of the multilayer ceramic capacitor 100 are shown in the figures, and these directions may be referred to in the following description. In this embodiment, the stacking direction of the ceramic layer 1a, which will be described later, is defined as the height direction T of the multilayer ceramic capacitor 100.

[0027] The multilayer ceramic capacitor 100 comprises a ceramic element 1 having a rectangular parallelepiped shape. The ceramic element 1 has a first main surface 1A and a second main surface 1B facing each other in the height direction T, a first side surface 1C and a second side surface 1D facing each other in the width direction W perpendicular to the height direction T, and a first end surface 1E and a second end surface 1F facing each other in the length direction L perpendicular to both the height direction T and the width direction W.

[0028] The ceramic body 1 includes a plurality of ceramic layers 1a stacked in the height direction T, a plurality of first internal electrodes 2, and a plurality of second internal electrodes 3. The first internal electrodes 2 are drawn out to the first end face 1E of the ceramic body 1. The second internal electrodes 3 are drawn out to the second end face 1F of the ceramic body 1.

[0029] The thickness of the ceramic layer 1a is arbitrary, but for example, in the volume forming section 11 described later, it can be about 0.3 μm to 2.0 μm.

[0030] The ceramic body 1 includes a capacitance-forming section 11 in which a first internal electrode 2 and a second internal electrode 3 are arranged opposite each other via a ceramic layer 1a, contributing to the formation of capacitance. The capacitance-forming section 11 is shown by a dashed line in Figures 2 and 3, respectively. The capacitance-forming section 11 has a rectangular parallelepiped shape with six faces.

[0031] The ceramic body 1 includes non-capacitance forming portions 12 formed on the outer sides of each of the six faces of the capacitance forming portion 11, where the first internal electrode 2 and the second internal electrode 3 are not arranged facing each other via the ceramic layer 1a and do not contribute to capacitance formation. The non-capacitance forming portions 12 formed on the outer sides of the first main surface 1A and the second main surface 1B of the capacitance forming portion 11 are sometimes called protective layers. The protective layers have a larger area than the capacitance forming portion 11 when viewed in the planar direction. The non-capacitance forming portions 12 formed on the outer sides of the first side surface 1C and the second side surface 1D of the capacitance forming portion 11 are sometimes called side gaps. The non-capacitance forming portions 12 formed on the outer sides of the first end surface 1E and the second end surface 1F of the capacitance forming portion 11 are sometimes called lead-out portions (lead-out portions of the internal electrodes).

[0032] The ceramic body 1 includes a surface protection layer 13 formed on at least a portion of the outside of the non-capacitance forming portion 12, and exposed on at least the first main surface 1A, the second main surface 1B, the first side surface 1C, and the second side surface 1D. In this embodiment, the surface protection layer 13 is formed on the outside of the first main surface 1A, the second main surface 1B, the first side surface 1C, and the second side surface 1D of the non-capacitance forming portion 12, but not on the outside of the first end surface 1E and the second end surface 1F of the non-capacitance forming portion 12. As will be described later, the ceramic composition constituting the surface protection layer 13 is different from the ceramic composition constituting the non-capacitance forming portion 12. The surface protection layer 13 is continuously formed on the outside of the first main surface 1A, the second main surface 1B, the first side surface 1C, and the second side surface 1D of the non-capacitance forming portion 12.

[0033] The ceramic constituting the capacitance-forming portion 11 of the ceramic substrate 1 is a ceramic with a composition suitable for exhibiting a good dielectric constant. The type of ceramic constituting the capacitance-forming portion 11 is arbitrary, but for example, a dielectric ceramic mainly composed of BaTiO3 can be used. In this embodiment, a dielectric ceramic mainly composed of BaTiO3 was used for the ceramic constituting the capacitance-forming portion 11. However, instead of BaTiO3, dielectric ceramics mainly composed of other materials such as CaTiO3, SrTiO3, or CaZrO3 may be used.

[0034] The type of ceramic constituting the non-capacitance forming portion 12 of the ceramic substrate 1 is arbitrary, but it is preferable to use the same ceramic as that constituting the capacitance forming portion 11. This is because using common materials simplifies material procurement, material processing, and material management, thereby improving productivity. In this embodiment, the ceramic constituting the non-capacitance forming portion 12 is a dielectric ceramic mainly composed of BaTiO3, the same as that used in the capacitance forming portion 11.

[0035] The ceramic used to constitute the surface protective layer 13 of the ceramic substrate 1 is a ceramic that exhibits high strength. The type of ceramic constituting the surface protective layer 13 is arbitrary, but in this embodiment, the main component of the ceramic constituting the surface protective layer 13 is a core-shell structure particle in which Zr (zirconium) is contained as a shell on the surface of BaTiO3. However, instead of (or in addition to) the core-shell structure particle in which Zr is contained as a shell on the surface of BaTiO3, a composite of ZrO2 (zirconium oxide; zirconia) and BaTiO3 may be used. Ceramics containing core-shell structure particles in which Zr is contained as a shell on the surface of BaTiO3, or ceramics consisting of a composite of ZrO2 and BaTiO3, can exhibit high strength.

[0036] The main metal components of the first internal electrode 2 and the second internal electrode 3 can be any type; for example, Ni can be used. However, other metals such as Cu, Ag, Pd, and Au may be used instead of Ni. Furthermore, Ni, Cu, Ag, Pd, and Au may be alloys with other metals. The thickness of the first internal electrode 2 and the second internal electrode 3 can be any thickness, but it is preferably about 0.1 to 2.0 μm.

[0037] The multilayer ceramic capacitor 100 has a first external electrode 4 formed on one end of the ceramic body 1 and a second external electrode 5 formed on the other end of the ceramic body 1. More specifically, the first external electrode 4 is formed on the first end face 1E of the ceramic body 1, and has a cap shape with its edges extending to the first main surface 1A, the second main surface 1B, the first side surface 1C, and the second side surface 1D, respectively. The second external electrode 5 is formed on the second end face 1F of the ceramic body 1, and has a cap shape with its edges extending to the first main surface 1A, the second main surface 1B, the first side surface 1C, and the second side surface 1D, respectively.

[0038] In Figures 2 and 3, the first external electrode 4 and the second external electrode 5 are shown as a single layer. However, generally, the first external electrode 4 and the second external electrode 5 are formed in multiple layers. The number of layers, materials, dimensions, and formation methods of the first external electrode 4 and the second external electrode 5 are arbitrary. In this embodiment, the first external electrode 4 and the second external electrode 5 are each formed in three layers: a base electrode layer mainly composed of Cu, formed by baking a Cu conductive paste; a Ni-plated electrode layer formed on the base electrode layer; and a Sn-plated electrode layer formed on the Ni-plated electrode layer. However, the main component of the base electrode layer may be, for example, Ni or Ag instead of Cu. Also, Cu, Ni, Ag, etc. may be alloys with other metals. In the first external electrode 4 and the second external electrode 5, the Ni-plated electrode layer is mainly provided to improve solder heat resistance and bonding performance. In the first external electrode 4 and the second external electrode 5, the Sn-plated electrode layer is provided primarily to improve solderability.

[0039] The first internal electrode 2 is electrically connected to the first external electrode 4. The second internal electrode 3 is electrically connected to the second external electrode 5.

[0040] In the multilayer ceramic capacitor 100 having the above configuration, different ceramic compositions are used for the surface protective layer 13 of the ceramic body 1 and for the capacitance-forming portion 11 and the non-capacitance-forming portion 12. Therefore, by using a ceramic composition that exhibits high strength in the surface protective layer 13, the strength of the ceramic body 1 can be maintained. Furthermore, because the multilayer ceramic capacitor 100 uses different ceramic compositions for the surface protective layer 13 of the ceramic body 1 and for the capacitance-forming portion 11 and the non-capacitance-forming portion 12, high capacitance can be achieved by using a ceramic composition that exhibits high dielectric constant in the capacitance-forming portion 11 and the non-capacitance-forming portion 12.

[0041] Furthermore, because the surface protective layer 13 of the ceramic element 1 of the multilayer ceramic capacitor 1 has high strength, cracks and fractures are less likely to occur in the ceramic element 1 even when external forces are applied to it, and it has high moisture resistance reliability.

[0042] It is preferable that the ceramic in the surface protective layer 13 of the multilayer ceramic capacitor 100 contains Zr (zirconia). Furthermore, it is preferable that the ceramic in the surface protective layer 13 of the multilayer ceramic capacitor 100 contains ZrO2 (zirconium oxide; zirconia), and it is even more preferable that the included ZrO2 is stabilized ZrO2. In these cases, even if an external force is applied to the ceramic body 1, the occurrence of cracks and chips in the ceramic body 1 due to stress-induced phase transitions of Zr or ZrO2 can be suppressed even more effectively.

[0043] The multilayer ceramic capacitor 100 can use a ceramic that contains particles with a core-shell structure, where Zr is included as a shell on the surface of BaTiO3, for the ceramic that constitutes the surface protective layer 13. Alternatively, the multilayer ceramic capacitor 100 can use a ceramic that contains a composite of ZrO2 and BaTiO3 for the ceramic that constitutes the surface protective layer 13. In these cases, a surface protective layer 13 with even higher strength can be formed.

[0044] In a multilayer ceramic capacitor 100, it is preferable that the average particle size of the ceramic constituting the surface protective layer 13 is smaller than the average particle size of the ceramic constituting the non-capacitance forming portion 12. This is because the strength of the surface protective layer 13 is further improved by forming it with ceramics that have a small average particle size. The average particle size of the ceramic constituting the surface protective layer 13 can be adjusted by adjusting the particle size and amount of the raw materials used to form the surface protective layer 13, as well as the type and amount of additives added to the raw materials.

[0045] The average particle size of the ceramics constituting the non-capacitance forming portion 12 and the surface protective layer 13 shall be measured by the following method. First, one surface is arbitrarily selected from the first main surface 1A, the second main surface 1B, the first side surface 1C, and the second side surface 1D of the ceramic body 1. Next, the thickness of the non-capacitance forming portion 12 and the thickness of the surface protective layer 13 are measured on the selected surface. Next, at the center of the selected surface (the point where the two diagonals intersect), a cross section parallel to the surface and with a depth of 1 / 2 of the total thickness of the surface protective layer 13 is cut out to obtain a 30 μm × 30 μm square area, which is designated as the measurement area for the surface protective layer 13. Similarly, at the center of the selected surface, a cross section parallel to the surface and with a depth of 1 / 2 of the total thickness of the non-capacitance forming portion 12 is cut out to obtain a 30 μm × 30 μm square area, which is designated as the measurement area for the non-capacitance forming portion 12. Next, the measurement area (cross-section) of the surface protective layer 13 is observed with an electron microscope, and 10 particles are selected in order from the largest diameter among the particles that appear in the measurement area. The average value of the diameters of these particles is then used as the average particle size of the ceramics constituting the surface protective layer 13. Similarly, the measurement area (cross-section) of the non-capacitance forming area 12 is observed with an electron microscope, and 10 particles are selected in order from the largest diameter among the particles that appear in the measurement area. The average value of the diameters of these particles is then used as the average particle size of the ceramics constituting the non-capacitance forming area 12.

[0046] The average particle size of the ceramic constituting the surface protective layer 13 is preferably 0.35 μm or less. This is because the surface protective layer 13 has high strength when the particle size is 0.35 μm or less.

[0047] In a multilayer ceramic capacitor 100, it is preferable that the pore ratio of the ceramic constituting the surface protection layer 13 is greater than the pore ratio of the ceramic constituting the non-capacitance forming portion 12. This is because a higher pore ratio of the ceramic constituting the surface protection layer 13 allows the pores (voids) contained in the surface protection layer 13 to disperse the stress applied to the ceramic body 1, thereby suppressing the propagation of stress to the non-capacitance forming portion 12 and the capacitance forming portion 11. The pore ratio of the ceramic constituting the surface protection layer 13 can be adjusted by adjusting the particle size and amount of the raw materials used to form the surface protection layer 13, as well as the type and amount of additives added to the raw materials.

[0048] The pore ratio of the ceramic constituting the non-capacitance forming portion 12 and the surface protective layer 13 shall be measured by the following method. First, one surface is arbitrarily selected from the first main surface 1A, the second main surface 1B, the first side surface 1C, and the second side surface 1D of the ceramic body 1. Next, the thickness of the non-capacitance forming portion 12 and the thickness of the surface protective layer 13 are measured on the selected surface. Next, a cross section parallel to the surface is cut out at the center of the selected surface to a depth of 1 / 2 of the total thickness of the surface protective layer 13, and a 1 μm × 1 μm square area is obtained and designated as the measurement area for the surface protective layer 13. Similarly, a cross section parallel to the surface is cut out at the center of the selected surface to a depth of 1 / 2 of the total thickness of the non-capacitance forming portion 12, and a 1 μm × 1 μm square area is obtained and designated as the measurement area for the non-capacitance forming portion 12. Next, the measurement area (cross-section) of the surface protective layer 13 is observed with an electron microscope, and the measurement area is divided into 100 × 100 = 10,000 sections. Of these 10,000 sections, those sections with a pore area of ​​50% or more are designated as pore sections. Then, the number of pore sections ÷ 10,000 × 100 (%) is roughly used as the pore ratio of the ceramic constituting the surface protective layer 13. Similarly, the measurement area (cross-section) of the non-capacitance forming section 12 is observed with an electron microscope, and the measurement area is divided into 100 × 100 = 10,000 sections. Of these 10,000 sections, those sections with a pore area of ​​50% or more are designated as pore sections. Then, the number of pore sections ÷ 10,000 × 100 (%) is roughly used as the pore ratio of the ceramic constituting the non-capacitance forming section 12.

[0049] In the multilayer ceramic capacitor 100, it is preferable that the average thickness of the surface protection layer 13 is between 1 μm and 10 μm. If the average thickness of the surface protection layer 13 is less than 1 μm, there is a risk that the protective function of the surface protection layer 13 on the ceramic body 1 will be insufficient. If the average thickness of the surface protection layer 13 exceeds 10 μm, the dimensions of the ceramic body 1 will become unnecessarily large. The average thickness of the surface protection layer 13 is calculated by measuring the thickness of the surface protection layer 13 at the center of each of the four surfaces of the ceramic body 1: the first main surface 1A, the second main surface 1B, the first side surface 1C, and the second side surface 1D, and averaging these four thicknesses.

[0050] (An example of a manufacturing method for a multilayer ceramic capacitor 100) The multilayer ceramic capacitor 100 can be manufactured, for example, by the following method.

[0051] First, ceramic powder, binder resin, solvent, etc. are prepared, and these are wet-mixed to produce a ceramic slurry. In this embodiment, BaTiO3 powder is used as the ceramic powder.

[0052] Next, a ceramic slurry is applied to a carrier film in a sheet-like manner using a die coater, gravure coater, microgravure coater, etc., and dried to produce a mother ceramic green sheet. In order to manufacture a large number of multilayer ceramic capacitors at once, the mother ceramic green sheet contains a matrix of numerous ceramic green sheets for multiple multilayer ceramic capacitors.

[0053] Next, a pre-prepared conductive paste is applied (e.g., printed) in a desired pattern shape to form the first internal electrode 2 on the main surface of a predetermined mother ceramic green sheet. Similarly, a pre-prepared conductive paste is applied in a desired pattern shape to form the second internal electrode 3 on the main surface of the predetermined mother ceramic green sheet. Note that conductive paste is not applied to the main surface of the predetermined mother ceramic green sheet for forming the protective layer. The conductive paste can be a mixture of, for example, metal powder (e.g., Ni powder), solvent, and binder resin.

[0054] Next, the three types of mother ceramic green sheets described above are stacked in a predetermined order and in a predetermined number of layers, then heated and pressed together to create an unfired mother ceramic body. The unfired mother ceramic body contains numerous unfired ceramic bodies in a matrix structure.

[0055] Next, the unfired mother ceramic body is cut into long strips to create a group of unfired long strip ceramic bodies. The group of unfired long strip ceramic bodies is formed such that the first main surface, second main surface, first side surface, and second side surface of each included unfired ceramic body are exposed to the outside, and the first end surface and second end surface of adjacent unfired ceramic bodies are connected.

[0056] Next, elemental powder and / or ceramic powder are attached to the outer surface of the unfired, elongated ceramic substrates. That is, raw materials for forming the surface protective layer 13 are attached to the outer surface of the unfired, elongated ceramic substrates. In this embodiment, Zr powder is used as the elemental powder and / or ZrO2 powder is used as the ceramic powder. Additives such as binder resin and solvents may be added to the powder to facilitate attachment.

[0057] Next, the group of unfired, elongated ceramic substrates is cut into individual unfired ceramic substrates. The first main surface, second main surface, first side surface, and second side surface of each unfired ceramic substrate have elemental powder (e.g., Zr powder) and / or ceramic powder (e.g., ZrO2 powder) attached to them. It is preferable to discard the unfired ceramic substrates at both ends of the group of unfired, elongated ceramic substrates, as unwanted powder may be attached to the first and second end surfaces.

[0058] Next, the unfired ceramic body is fired according to a predetermined profile to produce the ceramic body 1. At this time, elemental powder (Zr powder) and / or ceramic powder (ZrO2 powder) react with or mix with the ceramic contained in the unfired ceramic body (ceramic green sheet), forming a surface protection layer 13 on the first main surface 1A, second main surface 1B, first side surface 1C, and second side surface 1D of the ceramic body 1. Specifically, the surface protection layer 13 is formed by, for example, core-shell structure particles containing Zr as a shell on the surface of BaTiO3, or by ceramics containing a composite of ZrO2 and BaTiO3. However, the form of the ceramic constituting the surface protection layer 13 is not limited to these forms.

[0059] Next, a base electrode layer is formed by baking, for example, a Cu conductive paste onto both ends of the ceramic body 1, a Ni plated electrode layer is formed on the base electrode layer, and a Sn plated electrode layer is formed on the Ni plated electrode layer, thereby forming the first external electrode 4 and the second external electrode 5, and completing the multilayer ceramic capacitor 100.

[0060] [Second Embodiment] Figure 4 shows a multilayer ceramic capacitor 200 according to the second embodiment. However, Figure 4 is a perspective view of the multilayer ceramic capacitor 200.

[0061] The multilayer ceramic capacitor 200 according to the second embodiment has been modified in part to the configuration of the multilayer ceramic capacitor 100 according to the first embodiment. Specifically, in the multilayer ceramic capacitor 100, the surface protection layer 13 was formed on the first main surface 1A, the second main surface 1B, the first side surface 1C, and the second side surface 1D of the ceramic body 1. However, in the multilayer ceramic capacitor 200, this has been changed, and the surface protection layer 13 is formed on the first main surface 1A, the second main surface 1B, the first side surface 1C, the second side surface 1D, the first end surface, and the second end surface of the ceramic body 1. The surface protection layer 13 is continuously formed on the first main surface 1A, the second main surface 1B, the first side surface 1C, the second side surface 1D, the first end surface, and the second end surface of the ceramic body 1.

[0062] In one example of the manufacturing method for the multilayer ceramic capacitor 100 according to the first embodiment, powder that will form the surface protective layer 13 was attached to the outer surface of the group of unfired, elongated ceramic bodies at the stage of the group of unfired, elongated ceramic bodies. However, if this is changed, and the group of unfired, elongated ceramic bodies is cut into individual ceramic bodies, and then powder that will form the surface protective layer 13 is attached to the outer surface of each ceramic body, the surface protective layer 13 will be formed on the first and second end faces of the ceramic body 1, as in the multilayer ceramic capacitor 200.

[0063] In the second embodiment, the multilayer ceramic capacitor 200 also has improved strength at the first and second end faces of the ceramic element 1.

[0064] The first and second embodiments have been described above. However, the present invention is not limited to the above-described content, and various modifications can be made in accordance with the spirit of the invention.

[0065] For example, the materials of the ceramics constituting the volume-forming portion 11, the non-volume-forming portion 12, and the surface protective layer 13 of the ceramic body 1 described above are just examples, and other materials can also be used.

[0066] Furthermore, the form of the ceramic included in the surface protective layer 13 (such as a core-shell structure or composite) is just one example and is not limited to those described above.

[0067] A multilayer ceramic capacitor according to one embodiment of the present invention is as described in the "Means for Solving the Problem" section.

[0068] In this multilayer ceramic capacitor, it is also preferable that the composition of the ceramic constituting the capacitance-forming portion and the composition of the ceramic constituting the non-capacitance-forming portion are the same. In this case, the multilayer ceramic capacitor can be manufactured using one type of ceramic green sheet, thus improving productivity. Furthermore, material procurement, material processing, and material management become easier, further improving productivity.

[0069] It is also preferable that the ceramic constituting the surface protective layer contains Zr. For example, it is preferable that the ceramic constituting the surface protective layer contains ZrO2. It is also preferable that the ceramic constituting the surface protective layer contains particles with a core-shell structure in which Zr is included as a shell on the surface of BaTiO3. Furthermore, it is also preferable that the ceramic constituting the surface protective layer contains a composite of ZrO2 and BaTiO3. In these cases, even if an external force is applied to the ceramic body, the occurrence of cracks and chips in the ceramic body 1 due to stress-induced phase transitions of Zr or ZrO2 can be effectively suppressed.

[0070] It is preferable that the average particle size of the ceramic constituting the surface protective layer is smaller than the average particle size of the ceramic constituting the non-capacitance forming portion. In this case, the surface protective layer is formed of ceramic with a small average particle size, and the strength of the ceramic cutting is further improved.

[0071] It is also preferable that the average particle size of the ceramic constituting the surface protective layer is 0.35 μm or less. This is because the surface protective layer will have high strength in this case.

[0072] It is also preferable that the pore ratio of the ceramic constituting the surface protective layer is greater than that of the ceramic constituting the non-capacitance forming portion. In this case, the stress applied to the ceramic body can be dispersed by the pores (voids) contained in the surface protective layer, and the propagation of stress to the non-capacitance forming portion and the capacitive forming portion can be suppressed.

[0073] It is also preferable that the average thickness of the surface protective layer be between 1 μm and 10 μm. If the average thickness of the surface protective layer is less than 1 μm, there is a risk that the protective function of the surface protective layer on the ceramic body 1 will be insufficient. If the average thickness of the surface protective layer exceeds 10 μm, the dimensions of the ceramic body 1 will become unnecessarily large.

[0074] The method for manufacturing a multilayer ceramic capacitor according to one embodiment of the present invention is as described in the "Means for Solving the Problem" section.

[0075] In this method for manufacturing multilayer ceramic capacitors, it is also preferable that the elemental powder attached to the unfired ceramic body is Zr. Alternatively, it is also preferable that the ceramic powder attached to the unfired ceramic body is ZrO2. In these cases, a surface protective layer with high strength can be formed on the ceramic body.

[0076] 1…Ceramic base 1a. Ceramic layer 1A...First main surface 1B...Second main surface 1C...1st side 1D...Second side 1E...1st end surface 1F...2nd end surface 11...Capacitance forming part 12...Non-capacitance forming part 13...Surface protective layer 2...1st internal electrode 3...Second internal electrode 4...1st external electrode 5...Second external electrode

Claims

1. A ceramic body comprising a ceramic layer, a first internal electrode, and a second internal electrode, having a first main surface and a second main surface facing each other in the height direction, a first side surface and a second side surface facing each other in the width direction perpendicular to the height direction, and a first end surface and a second end surface facing each other in the length direction perpendicular to the height direction and the width direction, and stacked in the height direction, The ceramic body comprises a first external electrode and a second external electrode, The first internal electrode is electrically connected to the first external electrode, The second internal electrode is electrically connected to the second external electrode. It is a multilayer ceramic capacitor, The aforementioned ceramic material is A capacitance forming section in which the first internal electrode and the second internal electrode are arranged to face each other with respect to the ceramic layer, A non-capacitance forming portion in which the first internal electrode and the second internal electrode are not arranged facing each other with respect to the ceramic layer, A surface protective layer is provided which is located outside the non-capacitance forming portion and is exposed on the surface of the ceramic body, The composition of the ceramic constituting the surface protective layer is different from the composition of the ceramic constituting the non-capacitance forming portion. The surface protective layer is made of a ceramic including a composite of ZrO₂ and BaTiO₃, forming a multilayer ceramic capacitor.

2. A ceramic body comprising a ceramic layer, a first internal electrode, and a second internal electrode, having a first main surface and a second main surface facing each other in the height direction, a first side surface and a second side surface facing each other in the width direction perpendicular to the height direction, and a first end surface and a second end surface facing each other in the length direction perpendicular to the height direction and the width direction, and stacked in the height direction, The ceramic body comprises a first external electrode and a second external electrode, The first internal electrode is electrically connected to the first external electrode, The second internal electrode is electrically connected to the second external electrode. It is a multilayer ceramic capacitor, The aforementioned ceramic material is A capacitance forming portion between the internal electrode located on the first main surface side of the first internal electrode and the internal electrode located on the second main surface side of the first internal electrode and the second internal electrode, A non-capacitance forming portion is arranged outside the capacity forming portion, A surface protective layer is provided which is located outside the non-capacitance forming portion and is exposed on the surface of the ceramic body, The surface protective layer is made of a ceramic containing particles with a core-shell structure that includes Zr as a shell on the surface of BaTiO3. Multilayer ceramic capacitor.

3. The composition of the ceramic constituting the volume-forming portion and the composition of the ceramic constituting the non-volume-forming portion are the same. A multilayer ceramic capacitor according to claim 1 or claim 2.

4. The composition of the ceramic constituting the surface protective layer is different from the composition of the ceramic constituting the non-capacitance forming portion. A multilayer ceramic capacitor as described in claim 2.

5. The average particle size of the ceramic constituting the surface protective layer is smaller than the average particle size of the ceramic constituting the non-capacitance forming portion. A multilayer ceramic capacitor according to claim 1 or claim 2.

6. The average particle size of the ceramic constituting the surface protective layer is 0.35 μm or less. A multilayer ceramic capacitor according to claim 1 or claim 2.

7. The pore ratio of the ceramic constituting the surface protective layer is greater than the pore ratio of the ceramic constituting the non-capacitance forming portion. A multilayer ceramic capacitor according to claim 1 or claim 2.

8. The average thickness of the aforementioned surface protective layer is 1 μm or more and 10 μm or less. A multilayer ceramic capacitor according to claim 1 or claim 2.

9. A step of preparing an unfired ceramic body having a first main surface and a second main surface facing each other in the height direction, a first side surface and a second side surface facing each other in the width direction perpendicular to the height direction, and a first end surface and a second end surface facing each other in the length direction perpendicular to the height direction and the width direction, A step of attaching a powder, which is Zr or ZrO2, to the aforementioned unfired ceramic body, A step of firing the unfired ceramic body to which the powder is attached to produce a ceramic body, The process includes the step of forming an external electrode on the ceramic substrate. A method for manufacturing a multilayer ceramic capacitor, comprising the step of producing the ceramic body, which involves reacting a powder that is Zr or ZrO₂ with a ceramic contained in the unfired ceramic body to form a surface protective layer containing Zr.

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