Multilayer ceramic capacitor

Abstract

To provide a multilayer ceramic capacitor which has good characteristics such as an electrostatic capacitance, and has excellent reliability.SOLUTION: A multilayer ceramic capacitor 1 of a present disclosure contains: a lamination body 2 formed by alternately laminating a dielectric layer 5 and an internal electrode layer 6. The internal electrode layer 6 contains Ni as a main component, and includes a plurality of Li-containing parts 61 containing Li. Each of the plurality of Li-containing parts 61 is constructed by a Li single body or an alloy of Li and Ni.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This disclosure relates to multilayer ceramic capacitors. [Background technology]

[0002] In recent years, with the miniaturization and increased functionality of electronic devices, there has been a growing demand for miniaturization of electronic components used in these devices. For example, multilayer ceramic capacitors, a type of multilayer ceramic electronic component, are in need of further miniaturization and increased capacitance.

[0003] Multilayer ceramic capacitors include a laminate in which dielectric layers and internal electrode layers are alternately stacked. As multilayer ceramic capacitors become smaller and larger in capacitance, insulation degradation and a decrease in thermal shock resistance of the laminate are more likely to occur. Patent document 1 describes incorporating an Mg-Li-O crystalline oxide into the internal electrode layer in order to improve reliability such as thermal shock resistance while ensuring the characteristics of the multilayer ceramic capacitor. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2011-187560 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Conventional multilayer ceramic capacitors have room for improvement in terms of enhancing reliability while maintaining the characteristics of multilayer ceramic capacitors. [Means for solving the problem]

[0006] The multilayer ceramic capacitor of this disclosure includes a laminate in which dielectric layers and internal electrode layers are alternately stacked. The internal electrode layers are mainly composed of Ni and have a plurality of Li-containing portions containing Li. Each of the plurality of Li-containing portions is composed of Li alone or an alloy of Li and Ni. [Effects of the Invention]

[0007] The multilayer ceramic capacitors of this disclosure can improve reliability while ensuring the characteristics of a multilayer ceramic capacitor. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view showing a multilayer ceramic capacitor according to an embodiment of the present disclosure. [Figure 2] Figure 1 is a perspective view showing the main body of a multilayer ceramic capacitor. [Figure 3] This is a cross-sectional view taken from the line III-III in Figure 1. [Figure 4] This is a perspective view showing the process of creating a temporary laminate. [Figure 5] This is a perspective view showing the parent laminate. [Figure 6] This is a perspective view showing multiple main body parts obtained by cutting the parent laminate. [Figure 7] This is a perspective view showing the unfired main body. [Modes for carrying out the invention]

[0009] Embodiments of the multilayer ceramic capacitors of this disclosure will be described below with reference to the drawings. The drawings referenced below are schematic, and the dimensional ratios shown in the drawings are not necessarily accurate. In this specification, a Cartesian coordinate system XYZ is defined for convenience in some drawings. The X-axis direction is also referred to as the first direction or length direction. The Y-axis direction is also referred to as the second direction or width direction. The Z-axis direction is also referred to as the third direction, height direction, or stacking direction.

[0010] Figure 1 is a perspective view showing a multilayer ceramic capacitor according to an embodiment of the present disclosure; Figure 2 is a perspective view showing the laminate of the multilayer ceramic capacitor of Figure 1; and Figure 3 is a cross-sectional view taken along the line III-III of the cross section in Figure 1.

[0011] The multilayer ceramic capacitor 1 of this embodiment includes a laminate 2, as shown in Figure 1. The laminate 2 has a substantially rectangular parallelepiped shape, as shown in Figure 2. The laminate 2 has a first surface 7a and a second surface 7b facing each other in a third direction, a first end surface 8a and a second end surface 8b facing each other in a first direction, and a first side surface 9a and a second side surface 9b facing each other in a second direction. Hereinafter, the first surface 7a and the second surface 7b may be collectively referred to as main surfaces 7a and 7b, the first end surface 8a and the second end surface 8b may be collectively referred to as end surfaces 8a and 8b, and the first side surface 9a and the second side surface 9b may be collectively referred to as side surfaces 9a and 9b. The main surfaces 7a and 7b may be perpendicular to the third direction, the end surfaces 8a and 8b may be perpendicular to the first direction, and the side surfaces 9a and 9b may be perpendicular to the second direction.

[0012] As shown in Figure 3, the laminate 2 is constructed by alternately stacking dielectric layers 5 and internal electrode layers 6. The dielectric layers 5 and internal electrode layers 6 are stacked in a third direction. The internal electrode layers 6 are exposed on the first side surface 9a and the second side surface 9b. As shown in Figure 2, the ends of the internal electrode layers 6 exposed on the first side surface 9a and the ends exposed on the second side surface 9b are covered by the side margin portion 3 and are not exposed to the outside. In addition, the internal electrode layers 6 are exposed on either the first end surface 8a or the second end surface 8b depending on their polarity. As shown in Figure 3, the ends of the internal electrode layers 6 exposed on the first end surface 8a and the ends exposed on the second end surface 8b are covered by the first external electrode 4a and the second external electrode 4b, respectively, and are electrically connected to the first external electrode 4a and the second external electrode 4b.

[0013] The dielectric layer 5 is made of an insulating material. The dielectric layer 5 may be made of a ceramic material mainly composed of, for example, barium titanate (BaTiO3), calcium titanate (CaTiO3), strontium titanate (SrTiO3), barium zirconate (BaZrO3), etc. Hereinafter, unless otherwise specified, the dielectric layer 5 is assumed to be made of a ceramic material mainly composed of BaTiO3. In this specification, the "main component" refers to the component with the highest content ratio in the material or member under consideration. The content ratio may be, for example, weight% (wt%).

[0014] The dielectric layer 5 may contain metal elements such as magnesium (Mg), manganese (Mn), vanadium (V), and rare earth elements such as yttrium (Y), dysprosium (Dy), holmium (Ho), terbium (Tb), ytterbium (Yb). In this case, it is possible to improve the high-temperature load life and the temperature characteristics of the capacitance of the multilayer ceramic capacitor 1.

[0015] The internal electrode layer 6 is made of a conductive material mainly composed of nickel (Ni). As shown in FIG. 3, the internal electrode layer 6 has a plurality of Li-containing portions 61. As shown in FIG. 3, the Li-containing portions 61 of one layer of the internal electrode layer 6 may be in contact with both of the two layers of the dielectric layer 5 sandwiching the one layer of the internal electrode layer 6 in the third direction, or may be in contact with only one of them. The plurality of Li-containing portions 61 contain lithium (Li). Each of the plurality of Li-containing portions 61 is composed of Li alone or an alloy of Li and Ni (hereinafter also referred to as a Li-Ni alloy), and does not contain Li oxide (LiOx). The Li-containing portion 61 contains Li but substantially does not contain oxygen (O). The O concentration of the Li-containing portion 61 may be 0 ppm, or may be a value close to 0 ppm, such as less than 5 ppm, less than 10 ppm, etc.

[0016] The internal electrode layer 6 may contain Mg. In this case, the plurality of Li-containing portions 61 may include a Li-containing portion 61 composed of an alloy of Li, Ni, and Mg. Further, the internal electrode layer 6 may contain Mg and Mn. In this case, the plurality of Li-containing portions 61 may include a Li-containing portion 61 composed of an alloy of Li, Ni, Mg, and Mn. The Mg and Mn in the internal electrode layer 6 may be the Mg and Mn contained in the conductive material constituting the internal electrode layer 6. The Mg and Mn in the internal electrode layer 6 may be those in which the Mg and Mn contained in the ceramic material constituting the dielectric layer 5 have diffused when firing the unfired laminate 2.

[0017] The thinner the thickness of the dielectric layer 5, the more the capacitance of the multilayer ceramic capacitor 1 can be increased. The dielectric layer 5 may have a thickness of, for example, 0.1 μm or more and 10 μm or less. Also, as long as the characteristics as a multilayer ceramic capacitor can be ensured, the thinner the thickness of the internal electrode layer 6, the more internal defects caused by internal stress during firing or voltage application of the laminate 2 can be suppressed, and the reliability of the multilayer ceramic capacitor 1 can be improved. The internal electrode layer 6 may have a thickness of, for example, 1.5 μm or less.

[0018] As shown in FIG. 3, both ends in the third direction of the laminate 2 may be composed of a cover layer 21. The cover layer 21 is composed of an insulating material. The cover layer 21 may be composed of a ceramic material mainly composed of, for example, BaTiO3, CaTiO3, SrTiO3, BaZrO3, etc. The cover layer 21 may be composed of the same ceramic material as the ceramic material constituting the dielectric layer 5.

[0019] As shown in Figure 2, the side margin portion 3 is located on the first side surface 9a and the second side surface 9b of the laminate 2. The side margin portion 3 has an outer surface 3a opposite to the surface facing the laminate 2. The side margin portion 3 electrically insulates the ends of the internal electrode layers 6 with different polarities that are exposed on the sides 9a and 9b. In addition, the side margin portion 3 physically protects the ends of the internal electrode layers 6 that are exposed on the sides 9a and 9b. Hereafter, the laminate 2 and the side margin portion 3 may be collectively referred to as the main body portions 2 and 3.

[0020] The side margin portion 3 is made of an insulating material. The side margin portion 3 may also be made of a ceramic material. In this case, the side margin portion 3 can have insulating properties and relatively high mechanical strength. Furthermore, if the side margin portion 3 is made of a ceramic material, it becomes possible to fire the laminate 2 and the side margin portion 3 simultaneously. The side margin portion 3 may be made of a ceramic material mainly composed of, for example, BaTiO3, CaTiO3, SrTiO3, BaZrO3, etc. The side margin portion 3 may also be made of the same ceramic material as the ceramic material that constitutes the dielectric layer 5. In this case, as described later, it becomes possible to produce multiple main body portions 2 and 3 by cutting the master laminate. Note that in Figure 1, the boundary between the laminate 2 and the side margin portion 3 is shown by a dashed line, but the actual boundary is not clearly visible.

[0021] The thinner the side margin portion 3, the smaller and larger the multilayer ceramic capacitor 1 can be. The side margin portion 3 may have a thickness of, for example, about 30 μm or less.

[0022] As shown in Figures 1 and 3, the multilayer ceramic capacitor 1 further comprises a first external electrode 4a and a second external electrode 4b. The first external electrode 4a is located from the first end face 8a to the first surface 7a, the second surface 7b, and the outer surface 3a. The first external electrode 4a is electrically connected to the internal electrode layer 6 exposed on the first end face 8a. The second external electrode 4b is located from the second end face 8b to the first surface 7a, the second surface 7b, and the outer surface 3a. The second external electrode 4b is electrically connected to the internal electrode layer 6 exposed on the second end face 8b. Hereafter, the first external electrode 4a and the second external electrode 4b may be collectively referred to as external electrodes 4a and 4b.

[0023] The external electrodes 4a and 4b are composed of one or more conductive layers. The external electrodes 4a and 4b may also include a first layer 41 and a second layer 42, as shown in Figure 3. The first layer 41 is also called the base layer. The second layer 42 is also called the outer layer. The base layer 41 is in direct contact with the main body parts 2 and 3 and is connected to the ends of the internal electrode layer 6 that are exposed on the end faces 8a and 8b. The outer layer 42 covers the side of the base layer 41 opposite to the laminate 2 side. By composing the external electrodes 4a and 4b with multiple conductive layers, the adhesion between the external electrodes 4a and 4b and the main body parts 2 and 3 can be improved. Furthermore, the wettability of the external electrodes 4a and 4b to the conductive bonding material used when mounting the multilayer ceramic capacitor 1 to a substrate can be improved. As a result, the reliability of the multilayer ceramic capacitor 1 and the mounting structure including the multilayer ceramic capacitor 1 can be improved.

[0024] The base layer 41 is composed of a metallic material. Examples of metallic materials used for the base layer 41 include metals such as Ni, Cu, Ag, Pd, and Au, or alloys made of these metals. The base layer 41 may be formed using thin-film formation techniques such as plating, sputtering, and vapor deposition, or it may be formed using thick-film formation techniques such as dip lithography, screen printing, and gravure printing.

[0025] The outer layer 42 is made of a metallic material. Examples of metallic materials used for the outer layer 42 include metals such as Ni, Cu, Au, and Sn. The outer layer 42 may be formed using thin-film formation techniques such as electroless plating or electrolytic plating.

[0026] As described above, the multilayer ceramic capacitor 1 has an internal electrode layer 6 that is mainly composed of Ni and has multiple Li-containing portions 61, and these multiple Li-containing portions 61 do not contain Li oxide (LiOx). The specific heat capacity of Ni is about 440 J / kg / °C, while the specific heat capacity of Li is about 3582 J / kg / °C. Therefore, when the internal electrode layer 6 has multiple Li-containing portions 61, the specific heat capacity can be increased compared to when the internal electrode layer is composed only of Ni. Also, for example, the specific heat capacity of lithium oxide (LiOx) is about 1810 J / kg / °C, and the specific heat capacity of Li oxide (LiOx) tends to be smaller than the specific heat capacity of Li (about 3582 J / kg / °C). Therefore, when the internal electrode layer 6 has multiple Li-containing portions 61, the specific heat capacity can be increased compared to when the internal electrode layer contains Li oxide (LiOx). Thus, the multilayer ceramic capacitor 1 can suppress the temperature rise of the laminate 2 even when a heat source (for example, an internal combustion engine or motor in a vehicle) is present near the multilayer ceramic capacitor 1. As a result, the movement of oxygen vacancies in the dielectric layer 5 can be suppressed, thereby reducing the insulation degradation of the laminate 2 due to the generation of leakage current.

[0027] The multilayer ceramic capacitor 1 may have a configuration in which the average size of multiple Li-containing portions 61 in the direction along the internal electrode layer 6 (i.e., the XY plane direction) is 1 μm or more and 10 μm or less. The size of each Li-containing portion 61 can be calculated, as described in the examples, by obtaining an elemental mapping image of the cross-section of the internal electrode layer 6 using focused ion beam mass spectrometry (FIB-MS) and based on the Li and Ni concentrations obtained from the elemental mapping image.

[0028] The thermal expansion coefficient of Ni is 15 × 10 -6 ~53×10 -6 The temperature is approximately / °C, and the thermal expansion coefficient of BaTiO3 is 11 × 10⁻⁶. -6 While the thermal expansion coefficient is approximately / °C, the thermal expansion coefficient of Li is 56 × 10⁻⁶. -6 The temperature is approximately / °C. Since Li has a larger coefficient of thermal expansion than Ni and BaTiO3, if the average size of the multiple Li-containing portions 61 in the XY plane exceeds 10 μm, delamination of the laminate 2 is more likely to occur when the temperature of the laminate 2 rises. Also, if the average size of the multiple Li-containing portions 61 in the XY plane is less than 1 μm, the Li-containing portions 61 will not be able to effectively reduce the insulation degradation of the laminate 2. By keeping the average size of the multiple Li-containing portions 61 in the direction along the internal electrode layer 6 between 1 μm and 10 μm, it is possible to reduce the insulation degradation of the laminate 2 while suppressing the decrease in capacitance, and further suppress the delamination of the laminate 2. In other words, it is possible to improve reliability while ensuring the characteristics of a multilayer ceramic capacitor.

[0029] The multilayer ceramic capacitor 1 may have a configuration in which the area ratio of multiple Li-containing portions 61 to the area of ​​the internal electrode layer 6 in the cross-section of the laminate 2 is 0.2% or more and 1.0% or less. The cross-section of the laminate 2 may be a cross-section along the third direction (i.e., the lamination direction between the dielectric layer 5 and the internal electrode layer 6). Since Li has a larger coefficient of thermal expansion than Ni and BaTiO3, if the area ratio of the Li-containing portions 61 exceeds 1.0%, delamination of the laminate 2 is more likely to occur when the temperature of the laminate 2 rises. Also, if the area ratio of the Li-containing portions 61 is less than 0.2%, the Li-containing portions 61 will not be able to effectively reduce the insulation degradation of the laminate 2. By having an area ratio of Li-containing portions 61 of 0.2% or more and 1.0% or less, it is possible to reduce the insulation degradation of the laminate 2 while suppressing the decrease in capacitance, and further suppress the delamination of the laminate 2. In other words, it is possible to improve reliability while ensuring the characteristics of a multilayer ceramic capacitor.

[0030] Next, the manufacturing method of the multilayer ceramic capacitor 1 will be described. Figure 4 is a perspective view showing the process of fabricating a temporary laminate, Figure 5 is a perspective view showing the master laminate, Figure 6 is a perspective view showing multiple main body parts obtained by cutting the master laminate, and Figure 7 is a perspective view showing the unfired main body parts.

[0031] First, a raw material powder mainly composed of dielectric materials such as BaTiO3, CaTiO3, SrTiO3, or mixtures thereof is prepared as the material for the dielectric layer 5. Magnesium carbonate (Mg2CO3) powder, dysprosium oxide (Dy2O3) powder, manganese carbonate (MnCO3) powder, glass powder, etc., may be added to the raw material powder. The glass powder may be, for example, an SiO2-BaO-CaO type glass powder. Next, an organic vehicle is mixed with the prepared raw material powder to prepare a ceramic slurry. The organic vehicle used to prepare the ceramic slurry may be, for example, a resin such as a butyral resin dissolved in a solvent mixed with ethyl alcohol and toluene. Subsequently, a ceramic green sheet (hereinafter simply referred to as a green sheet) 13, which will become the dielectric layer 5, is formed using the prepared ceramic slurry by a sheet forming method such as the doctor blade method or the die coater method. The average thickness of the green sheet 13 may be, for example, about 0.5 to 10 μm. In the manufacturing method described here, the green sheet 13 not only constitutes the dielectric layer 5 but also the side margin portion 3.

[0032] Next, as the material for the internal electrode layer 6, a Ni paste is prepared using a Ni-based powder and an organic vehicle, and a conductive paste is prepared by mixing Li and a dispersant into the Ni paste. The organic vehicle used to prepare the Ni paste may be, for example, a resin such as ethyl cellulose dissolved in a solvent which is a mixture of a dihydroterpineol-based solvent and butyl cellosolve. When preparing the conductive paste, Li powder may be added to the Ni paste, or a compound containing Li may be added to the Ni paste. The form of the compound containing Li may be a Li sol. The Li sol may contain carbon (C). In this case, when the laminate 2 is fired, C acts as a reducing agent, so the formation of Li oxide in the internal electrode layer 6 can be suppressed. As a result, the insulation degradation of the laminate 2 can be reduced. The dispersant may be, for example, oleic acid or polyethylene glycol. In this case, when the laminate 2 is fired, the C contained in the dispersant acts as a reducing agent, so the formation of Li oxide in the internal electrode layer 6 can be suppressed. As a result, the insulation degradation of the laminate 2 can be reduced.

[0033] Next, a pattern sheet 14 is formed on the main surface of the green sheet 13 using conductive paste, with an electrode pattern that will become the internal electrode layer 6 printed on it (see Figure 4). The electrode pattern can be printed using a printing method such as screen printing or gravure printing.

[0034] Next, as shown in Figure 4, a temporary laminate is created by stacking a predetermined number of pattern sheets 14 on top of a predetermined number of stacked green sheets 13, and then stacking a predetermined number of green sheets 13 again. The predetermined number of stacked green sheets 13 become the cover layer 21. By applying pressure to the temporary laminate in the stacking direction, a base laminate 15 as shown in Figure 5 is obtained. The temporary laminate can be applied using, for example, a hydrostatic press. Subsequently, the base laminate 15 is cut along a virtual dividing line 16 to produce multiple unfired main body parts 2 and 3 as shown in Figure 6. The base laminate 15 can be cut using, for example, a press-cutting machine, a dicing saw, etc. Figure 7 shows the unfired main body parts 2 and 3. Since the unfired main body parts 2 and 3 have the same structure as the fired main body parts 2 and 3, the terms and reference numerals such as dielectric layer 5, internal electrode layer 6, main surfaces 7a and 7b, end surfaces 8a and 8b, and side surfaces 9a and 9b will also be used for the unfired main body parts 2 and 3 below.

[0035] Next, the main body parts 2 and 3 are degreased in an atmospheric atmosphere, an inert gas atmosphere, or a reducing atmosphere. The degreasing treatment may be carried out under atmospheric pressure or under reduced pressure.

[0036] Next, the degreased main body parts 2 and 3 are fired in a reducing atmosphere. The atmosphere gas may be, for example, a mixture of hydrogen (H2) and nitrogen (N2). The firing temperature may be, for example, around 1100 to 1300°C, and the heating rate may be, for example, around 8000 to 12000°C / Hr. By setting the heating rate to a relatively high speed, the diffusion of Li contained in the conductive paste into the dielectric layer 5 can be suppressed. As a result, the decrease in capacitance can be reduced.

[0037] Next, the main body parts 2 and 3 after firing are subjected to a re-oxidation treatment in an O2 (oxygen) atmosphere. The temperature for the re-oxidation treatment may be, for example, around 800 to 1000°C. The equilibrium partial pressure of oxygen is, for example, 10 -12 ~10 -8 It can be around atm. The equilibrium partial pressure of oxygen is 10 -12If it is lower than the atm level, the dielectric layer 5 is not sufficiently re-oxidized, and as a result, insulation degradation of the laminate 2 may easily occur, or the capacitance of the multilayer ceramic capacitor 1 may decrease. Also, when the equilibrium partial pressure of oxygen is higher than about 10 -8 atm, Li contained in the internal electrode layer 6 is likely to be oxidized, and Li oxide (LiOx) is likely to occur. As a result, for example, when a heat source exists near the multilayer ceramic capacitor 1, the temperature of the dielectric layer 5 is likely to rise, and insulation degradation may easily occur. By setting the equilibrium partial pressure of oxygen to about 10 -12 ~10 -8 atm, the occurrence of insulation degradation and the decrease in capacitance can be suppressed.

[0038] Next, the barrel polishing process is performed on the main body parts 2 and 3 after the re-oxidation process to sufficiently expose the internal electrode layer 6 on the end faces 8a and 8b, and by removing the burrs of the main body parts 2 and 3, the main body parts 2 and 3 as shown in FIG. 2 are obtained. By forming the external electrodes 4a and 4b on the obtained main body parts 2 and 3, the multilayer ceramic capacitor 1 can be manufactured. Note that the external electrodes 4a and 4b may be formed by applying a conductive paste that becomes the external electrodes 4a and 4b to the unfired main body parts 2 and 3 and co-firing the main body parts 2 and 3 and the external electrodes 4a and 4b.

[0039] The above describes an example in which the main body parts 2 and 3 are obtained by cutting the master laminate 15, but the method of manufacturing the main body parts 2 and 3 is not limited to this. The main body parts 2 and 3 may be manufactured, for example, by cutting the master laminate 15 to manufacture the laminate 2, and then forming the side margin parts 3 on the sides 9a and 9b of the laminate 2. When the laminate 2 is manufactured in this way, the electrode pattern of the pattern sheet 14 may differ from the electrode pattern shown in Figure 4. The side margin parts 3 may be formed, for example, by molding a ceramic green sheet for the side margin parts (hereinafter also referred to as the green sheet for the side margin parts) using a ceramic slurry similar to the ceramic slurry used to mold the green sheet 13, and then pressing the green sheet for the side margin parts onto the sides 9a and 9b. In order to increase the adhesion of the green sheet for the side margin parts to the sides 9a and 9b, at least one of the laminate 2 and the green sheet for the side margin parts may be heated when pressing the green sheet for the side margin parts onto the sides 9a and 9b. Alternatively, the green sheet for the side margin may be made tacky, and the green sheet for the side margin may be bonded to the sides 9a and 9b using an adhesive that does not affect the characteristics of the multilayer ceramic capacitor 1. The side margin 3 may also be formed by applying the ceramic slurry prepared for molding the green sheet for the side margin to the sides 9a and 9b and drying it. [Examples]

[0040] The following describes examples of the multilayer ceramic capacitor 1, but the multilayer ceramic capacitor 1 of this disclosure is not limited to the following examples.

[0041] As an example, multilayer ceramic capacitors No. 4 to 9 shown in Tables 1 to 3 were fabricated. Multilayer ceramic capacitors No. 4 to 9 have the configuration shown in Figures 1 to 3. In addition, multilayer ceramic capacitors No. 1 to 3 shown in Tables 1 to 3 were fabricated as a comparative example. Samples No. 1 to 9 are 2012 type multilayer ceramic capacitors with a length of 2.0 mm and a width and thickness of 1.25 mm. The number of dielectric layers, thickness, etc. were set so that the capacitance of the multilayer ceramic capacitor would be 10,000 nF when the internal electrode layer is composed only of Ni. The fabrication conditions for samples No. 1 to 9 are shown in Table 1.

[0042] [Table 1]

[0043] The fabrication of multilayer ceramic capacitors 1 for samples No. 4 to 9 will be described. First, a ceramic slurry was prepared by mixing a raw material powder mainly composed of BaTiO3 with an organic vehicle. The raw material powder consisted of 100 moles of BaTiO3 powder, with 0.8 moles of Mg2CO3 powder (in terms of MgO), 0.8 moles of Dy2O3 powder, and 0.3 moles of MnCO3 powder (in terms of MnO), and further, 1 part by mass of glass powder per 100 parts by mass of BaTiO3 powder. A butyral-based resin was used as the resin to be included in the organic vehicle. The amount of butyral-based resin added was 10 parts by mass per 100 parts by mass of raw material powder. A solvent consisting of ethyl alcohol and toluene mixed in a 1:1 ratio was used. Next, a ceramic green sheet 13 with an average thickness of 2.8 μm was molded using the doctor blade method with the prepared ceramic slurry.

[0044] Next, a Ni paste was prepared using Ni powder. Ethyl cellulose was used as the resin for preparing the Ni paste. The amount of ethyl cellulose added was 5 parts by mass per 100 parts by mass of Ni powder. A mixture of dihydroterpineol-based solvent and butyl cellosolve was used as the solvent. Subsequently, a conductive paste was prepared by adding Li sol and a dispersant to the prepared Ni paste. A mixture of lithium alkoxide (CH3OC2H4OLi), 2-methoxyethanol (CH3OC2H4OH), and ethanol (C2H5OH) was used as the Li sol. NAA(registered trademark)-35 (manufactured by NOF Corporation) was used as the dispersant. The Li sol and dispersant were added so that the Li sol (Li equivalent) was 0.1 to 0.6 wt% and the dispersant was 1.0 to 1.5 wt% relative to the Ni paste (Ni equivalent). Using the prepared conductive paste, an electrode pattern that would become the internal electrode layer 6 was printed on the main surface of the green sheet 13 to form a pattern sheet 14.

[0045] Next, a base laminate was prepared using green sheet 13 and pattern sheet 14. 200 sheets of pattern sheet 14 were laminated. Subsequently, the base laminate was cut using a press-cutting machine to produce multiple main body parts 2 and 3.

[0046] Next, the main body parts 2 and 3 were degreased, and the degreased main body parts 2 and 3 were reduced and fired in an H2-N2 mixed gas atmosphere. The firing temperature was 1100°C, and the heating rate was 10000°C / Hr. Subsequently, the fired main body parts 2 and 3 were re-oxidized in an O2 atmosphere. The re-oxidation temperature was 1000°C, and the equilibrium partial pressure of O2 was 10 -11 The temperature was set to atm. The main body parts 2 and 3, which had undergone re-oxidation treatment, were barrel polished, and external electrodes 4a and 4b were formed on the polished main body parts 2 and 3 to fabricate the multilayer ceramic capacitors 1 of samples No. 4 to 9.

[0047] Next, the fabrication of the multilayer ceramic capacitors No. 1 to 3 will be described. The multilayer ceramic capacitor No. 1 was fabricated in the same manner as samples No. 4 to 9, except that Li was not added to the Ni paste when preparing the conductive paste. The multilayer ceramic capacitor No. 2 was fabricated in the same manner as samples No. 4 to 9, except that lithium carbonate (Li2CO3) was added to the Ni paste instead of Li sol when preparing the conductive paste. The multilayer ceramic capacitor No. 3 was fabricated in the same manner as samples No. 4 to 9, except that the heating rate was set to 3000°C / Hr when firing the main body parts 2 and 3.

[0048] The structure of the internal electrode layer in multilayer ceramic capacitors No. 1 to 9 will be described.

[0049] [Table 2]

[0050] Each of the samples No. 1 to 9 was cut along the third direction to expose the cut surface as shown in Figure 3, and the cut surface was polished using abrasive paper, a hard buff, and a soft buff. Next, the polished cut surface was observed using FIB-MS. A 60 μm square area on the cut surface was magnified 1500 to 1900 times, and mapping images of Ni and Li were obtained. Based on the obtained mapping images, the region where Li is present in the internal electrode layer 6 was detected. In addition, the area of ​​the internal electrode layer was calculated based on the SIM (Scanning Ion Microscope) image obtained by detecting secondary electrons generated by irradiation with a focused ion beam.

[0051] Next, a mapping image (hereinafter also referred to as the magnified mapping image) was obtained by magnifying a 10 μm square area containing the region where Li is present by 8,000 to 11,000 times. Based on the magnified mapping image, the average size of the Li-containing portion 61 in the XY plane (hereinafter also simply referred to as the average size of the Li-containing portion 61) and the area of ​​the Li-containing portion 61 were calculated.

[0052] In calculating the average size and area of ​​the Li-containing portion 61, Li-containing regions with a Li concentration of 100 ppm or more, a Ni concentration of less than 10 ppm and an O concentration of less than 10 ppm, or a Li concentration of 100 ppm or more, a Ni concentration of 100 ppm or more and an O concentration of less than 10 ppm were detected. The average size of the Li-containing region was taken as the average size of the Li-containing portion 61 (see "Average Size of Li-containing Portion" in Table 1), and the area of ​​the Li-containing region was taken as the area of ​​the Li-containing portion 61. Furthermore, the area ratio of the Li-containing portion 61 within a 60 μm square area of ​​the cross-section was calculated by dividing the area of ​​the Li-containing portion 61 by the area of ​​the internal electrode layer 6 (see "Area Ratio of Li-containing Portion" in Table 1).

[0053] Based on the magnified mapping image, the average size of Li oxide (LiOx) in the XY plane (hereinafter also simply referred to as the average size of Li oxide) and the area of ​​Li oxide were calculated. Li-O-containing regions with a Li concentration of 100 ppm or more and an O concentration of 100 ppm or more were detected, and the average size of the Li-O-containing region was taken as the average size of Li oxide (shown in Table 1 as "Average Size of Li Oxide"), and the area of ​​the Li-O-containing region was taken as the area of ​​Li oxide. The area of ​​Li oxide was divided by the area of ​​the internal electrode layer to calculate the area ratio of Li oxide in a 60 μm square area of ​​the cross-section (shown in Table 1 as "Li Oxide Area Ratio").

[0054] This section describes the capacitance, mean time to failure, and thermal shock resistance of multilayer ceramic capacitors No. 1 to 9.

[0055] (Capacitance) Capacitance was measured for samples No. 1 to 9. The measurement conditions were an ambient temperature of 20°C, a frequency of 120 Hz, and an applied voltage of 0.5 Vrms. Capacitance was measured using an LCR meter. For each of samples No. 1 to 9, 20 multilayer ceramic capacitors were fabricated, and the average capacitance of these capacitors was taken as the capacitance (nF) of each sample. The results are shown in Table 3.

[0056] [Table 3]

[0057] Samples No. 1 and Nos. 4-9 all have a capacitance of 10,000 nF, achieving the capacitance as designed. Samples Nos. 2 and 3 have a capacitance that is lower than 10,000 nF. In sample No. 2, the internal electrode layer contains insulating Li oxide, which is thought to have reduced the area of ​​the internal electrode layer that contributes to capacitance acquisition, thus lowering the capacitance. In sample No. 3, the heating rate during firing of the main body was lower compared to samples Nos. 4-9, which is thought to have caused Li to diffuse into the dielectric layer, resulting in a decrease in capacitance.

[0058] (Mean failure time) Highly Accelerated Life Tests (HALTs) were performed on samples No. 1 to 9, and the Mean Time To Failure (MTTF) was measured. The test conditions were an ambient temperature of 170°C and an applied DC voltage of 45V. For each of samples No. 1 to 9, 100 multilayer ceramic capacitors were fabricated, and the time when 50 multilayer ceramic capacitors failed was defined as the MTTF (Hr). The results are shown in Table 3.

[0059] Sample No. 1 has a shorter MTTF than samples No. 2-9. Sample No. 1's internal electrode layer is composed solely of Ni. Li plays a role in lowering the firing temperature, but since sample No. 1 does not contain Li, the firing temperature needs to be increased. Increasing the firing temperature promotes BaTiO3 grain growth, which increases the size of the BaTiO3 grains and is thought to reduce the reliability of the multilayer ceramic capacitor. Samples No. 2 and 3 contain Li, so compared to sample No. 1, the firing temperature can be lowered to suppress BaTiO3 grain growth, which is thought to improve the reliability of the multilayer ceramic capacitor. Samples No. 4-9 also contain Li, so compared to sample No. 1, the firing temperature can be lowered to suppress BaTiO3 grain growth, which improves the reliability of the multilayer ceramic capacitor. Furthermore, since samples No. 4 to 9 do not have Li oxide in their internal electrode layers and instead contain Li-containing portions (elemental Li or Li-Ni alloy), the temperature of the internal electrode layer is less likely to rise compared to samples No. 1 to 3, and insulation degradation is less likely to occur. Comparing samples No. 4 to 8 with each other, it is thought that as the amount of Li in the conductive paste increases, the area ratio of the Li-containing portion increases, making insulation degradation less likely to occur (i.e., the MTTF becomes longer).

[0060] Comparing sample No. 7 and sample No. 8, the manufacturing conditions were the same except for the amount of dispersant (see Table 1). Sample No. 8 had a smaller average size of the Li-containing portion and a longer MTTF than sample No. 7. This is thought to be because sample No. 8 had a larger amount of dispersant in the conductive paste that formed the internal electrode layer than sample No. 7, resulting in a relatively smaller average size of Li-containing portion being dispersed within the internal electrode layer. As a result, delamination of the laminate was suppressed, and the MTTF was improved.

[0061] Comparing sample No. 8 and sample No. 9, the area ratio of the Li-containing portion is almost the same, but sample No. 8 has a smaller average size of the Li-containing portion and a longer MTTF than sample No. 9. It is thought that because sample No. 8 has a larger amount of dispersant in the conductive paste that forms the internal electrode layer than sample No. 9, the relatively small average size of the Li-containing portion is dispersed in the internal electrode layer, which suppresses delamination of the laminate and improves the MTTF.

[0062] (Thermal shock resistance) Thermal shock resistance tests were conducted on samples No. 1 to 9 to evaluate their thermal shock resistance. For each of samples No. 1 to 9, 100 multilayer ceramic capacitors were fabricated and immersed in a solder bath maintained at a temperature of 305°C for 5 seconds. After removal from the solder bath, the number of multilayer ceramic capacitors with cracks was counted by visual inspection. The results are shown in Table 3. No cracks were observed in samples No. 1 to 8, but cracks were observed in two multilayer ceramic capacitors of sample No. 9. It is thought that sample No. 9 has a larger amount of Li in the conductive paste than samples No. 1 to 8, resulting in a larger average size of the Li-containing portion, and consequently, a lower thermal shock resistance compared to samples No. 1 to 8.

[0063] Although embodiments of this disclosure have been described in detail above, this disclosure is not limited to the embodiments described above, and various modifications and improvements are possible without departing from the gist of this disclosure. [Explanation of symbols]

[0064] 1. Multilayer ceramic capacitor 2 Laminate 21 Cover layer 3. Side margin section 3a External surface 4a 1st external electrode 4b 2nd external electrode 41 1st layer (base layer) 42 2nd layer (outer layer) 5. Dielectric layer 6 Internal electrode layer 61 Li-containing part 7a 1st page 7b 2nd side 8a 1st end face 8b 2nd end face 9a 1st side 9b Second side 13 Ceramic Green Sheet 14 Pattern Sheets 15 Mother laminate 16 virtual partition lines

Claims

1. The laminate includes a dielectric layer and an internal electrode layer that are alternately stacked, The internal electrode layer has Ni as its main component and has a plurality of Li-containing portions containing Li. A multilayer ceramic electronic component in which each of the plurality of Li-containing portions is composed of Li alone or an alloy of Li and Ni.

2. The multilayer ceramic capacitor according to claim 1, wherein the average size of the plurality of Li-containing portions in the direction along the internal electrode layer is 1 μm or more and 10 μm or less.

3. The multilayer ceramic capacitor according to claim 1 or 2, wherein in the cross-section of the laminate, the area ratio of the plurality of Li-containing portions to the area of ​​the internal electrode layer is 0.2% or more and 1% or less.

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