Manufacturing method for multilayer ceramic capacitors

Abstract

To provide a multi-layer ceramic capacitor and a method for producing the same.SOLUTION: A production method comprises: forming ceramic dielectric layers and internal electrode layers produced from specific metal particles; alternately laminating the internal electrode layers and the ceramic dielectric layers to form a laminate; applying a sintering process to the laminate to form a laminated ceramic body; and forming terminal electrodes on both ends of the laminated ceramic body to obtain the multi-layer ceramic capacitor. The produced multi-layer ceramic capacitor has excellent continuity of the internal electrode and favorable capacitor properties and reliability.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a multilayer ceramic capacitor, and more particularly to a multilayer ceramic capacitor having high internal electrode continuity and a method for manufacturing the same. [Background technology]

[0002] With advances in science and technology, the requirements for capacitors in electronic products are becoming increasingly stringent. Research and development is focused on thinner and lighter capacitors, and the size specifications for capacitors are becoming smaller and smaller. To meet both the size and capacitance requirements, multilayer ceramic capacitors (MLCCs), which have multiple metal electrode sheets, are becoming a product that is being actively developed. Multilayer ceramic capacitors are made by stacking energy storage materials in a comb structure, so they have a large electrode area for the same volume, providing favorable capacitance characteristics and meeting the application requirements of high-end products.

[0003] In the manufacturing process of a multilayer ceramic capacitor, the more the number of stacked internal electrode layers increases, the finer the internal electrode layers become. However, the high-temperature thermal energy applied in the sintering process causes the metal particles of the internal electrode layers to become spherical, which often leads to discontinuities and further reduces the capacitance characteristics of the multilayer ceramic capacitor. Summary of the Invention [Problem to be solved by the invention]

[0004] In view of this, it is urgently desired to provide a multilayer ceramic capacitor and a method for manufacturing the same that overcome the drawbacks of conventional multilayer ceramic capacitors and methods for manufacturing the same. [Means for solving the problem]

[0005] One aspect of the present invention provides a method for manufacturing a multilayer ceramic capacitor that can effectively improve the continuity of the internal electrodes of the multilayer ceramic capacitor by forming internal electrode layers using specific metal particles.

[0006] Another aspect of the present invention provides a multilayer ceramic capacitor manufactured by the above-described method.

[0007] According to one aspect of the present invention, a method for manufacturing a multilayer ceramic capacitor is provided. This manufacturing method first forms a plurality of internal electrode layers, followed by a plurality of ceramic dielectric layers. Here, each internal electrode layer is made of a plurality of metal particles, and each of the metal particles includes a nickel metal core and a metal oxide layer. The metal oxide layer completely covers the nickel metal core. The internal electrode layers and the ceramic dielectric layers are then alternately stacked to form a laminate. Next, a sintering process is performed on the laminate to form a multilayer ceramic body. Here, the sintering process includes a low-temperature burn-off step and a high-temperature sintering step. During the high-temperature sintering step, the metal oxide layers of the metal particles are reduced to metal layers. Then, end electrodes are formed on both ends of the multilayer ceramic body, respectively, to obtain a multilayer ceramic capacitor.

[0008] According to some embodiments of the present invention, in the method for forming the metal particles, the atomized solution is first used as a carrier for nickel metal cores, and then the atomized solution containing the nickel metal cores is subjected to a film-forming process to form a metal oxide layer, and after the metal oxide layer is formed, a magnetic separation process is performed to obtain the metal particles.

[0009] According to some embodiments of the present invention, the atomized solution includes a compound having metal atoms corresponding to the metal oxide layer.

[0010] According to some embodiments of the present invention, the metal oxide layer has a thickness of 1 nm to 50 nm.

[0011] According to some embodiments of the present invention, the metal oxide layer comprises tin oxide and the metal layer comprises metallic tin.

[0012] According to some embodiments of the present invention, prior to the high temperature sintering step, the aforementioned internal electrode layers are not treated in a reducing environment.

[0013] According to some embodiments of the present invention, the oxygen partial pressure of the reducing environment is 10 -10 MPa or less.

[0014] According to some embodiments of the present invention, the temperature of said reducing environment is 1000° C. or higher.

[0015] According to some embodiments of the present invention, the oxygen partial pressure in the aforementioned high temperature sintering step is 10 -12 MPa~10 -10 MPa.

[0016] According to some embodiments of the present invention, the high-temperature sintering step includes a heating step, a temperature-maintaining step, and a cooling step, wherein the heating rate of the heating step is 30°C / min or more, the temperature-maintaining time of the temperature-maintaining step is 50 minutes or less, and the cooling rate of the cooling step is 10°C / min or more.

[0017] According to some embodiments of the present invention, when the aforementioned high-temperature sintering step is performed, oxygen vacancies are formed in each of the ceramic dielectric layers, and the oxygen vacancies are adjacent to the interfaces between each of the ceramic dielectric layers and each of the internal electrode layers.

[0018] According to some embodiments of the present invention, the thickness of each oxygen vacancy in the ceramic dielectric layer is 10 nm to 100 nm when calculated from this interface.

[0019] According to some embodiments of the present invention, the aforementioned interface forms a Schottky barrier.

[0020] According to another aspect of the present invention, there is provided a multilayer ceramic capacitor. This multilayer ceramic capacitor is manufactured by the above-mentioned manufacturing method, and includes a multilayer ceramic body and two end electrodes. The multilayer ceramic body includes a plurality of internal electrode layers and a plurality of ceramic dielectric layers that are alternately stacked with each other. The end electrodes are provided on both ends of the multilayer ceramic body. This multilayer ceramic capacitor has an internal electrode continuity of 85% or more.

[0021] According to some embodiments of the present invention, each of the aforementioned ceramic dielectric layers has oxygen vacancies, and the oxygen vacancies are adjacent to the interfaces between each of the ceramic dielectric layers and each of the internal electrode layers.

[0022] According to some embodiments of the present invention, the thickness of each oxygen vacancy in the ceramic dielectric layer is 10 nm to 100 nm, calculated from the aforementioned interface.

[0023] According to some embodiments of the present invention, the aforementioned interface is a Schottky barrier. [Effects of the Invention]

[0024] By applying the multilayer ceramic capacitor and its manufacturing method of the present invention, internal electrode layers can be formed from metal particles containing a nickel metal core and a metal oxide layer, and the metal oxide layer can be reduced in a subsequent sintering process to obtain internal electrode layers formed from a nickel alloy material. This reduces the difference in shrinkage between the internal electrode layers and the ceramic dielectric layers, thereby improving the internal electrode continuity of the multilayer ceramic capacitor. Furthermore, the nickel alloy particles specified in the present invention are useful for forming ceramic dielectric layers in semiconductor regions, thereby effectively suppressing leakage current at the interfaces between the internal electrode layers and the ceramic dielectric layers, further improving the long-term reliability of the multilayer ceramic capacitor. This allows the multilayer ceramic capacitor of the present invention to have favorable capacitance characteristics and reliability. [Brief explanation of the drawings]

[0025] For a more complete understanding of the embodiments of the present invention and its advantages, reference should be made to the following description taken in conjunction with the drawings. It should be emphasized that the various features are not drawn to scale, but are for illustrative purposes only. The contents of the associated drawings are described as follows: [Figure 1] 1 is a schematic cross-sectional view showing a multilayer ceramic capacitor according to some embodiments of the present invention. [Figure 2] 1 is a flowchart illustrating a method for manufacturing a multilayer ceramic capacitor according to some embodiments of the present invention. [Figure 3A] 3 is a scanning electron microscope photograph showing metal particles in the internal electrode layer according to Example 1 of the present invention. [Figure 3B] 3 is a transmission electron microscope photograph showing metal particles in an internal electrode layer according to Example 1 of the present invention. [Figure 4] 10 is a transmission electron microscope photograph showing metal particles in an internal electrode layer according to Example 2 of the present invention. [Figure 5A] 1 is an optical microscope photograph showing a cross section of a multilayer ceramic body of a multilayer ceramic capacitor according to Example 1 of the present invention at a high magnification. [Figure 5B] 10 is an optical microscope photograph showing a cross section of a multilayer ceramic body of a multilayer ceramic capacitor according to Example 2 of the present invention at a high magnification. [Figure 5C] 1 is an optical microscope photograph showing a cross section of a multilayer ceramic body of a multilayer ceramic capacitor according to Comparative Example 1 of the present invention at a high magnification. [Figure 5D] 10 is an optical microscope photograph showing a cross section at a high magnification of a multilayer ceramic body of a multilayer ceramic capacitor according to Comparative Example 2 of the present invention. [Figure 6A] 1 is a scanning transmission electron microscope photograph showing a multilayer ceramic body of a multilayer ceramic capacitor according to Example 1 of the present invention. [Figure 6B] FIG. 6A shows a spatially resolved electron energy loss spectrogram. [Figure 7A] 1 is a scanning transmission electron microscope photograph showing a multilayer ceramic body of a multilayer ceramic capacitor according to Comparative Example 1 of the present invention. [Figure 7B] FIG. 7A shows a spatially resolved electron energy loss spectrogram. [Figure 8A] The near-field structure diagram of the electron energy loss according to FIG. 6B is shown. [Figure 8B] A diagram of the vicinity structure of electron energy loss according to FIG. 7B is shown. DETAILED DESCRIPTION OF THE INVENTION

[0026] For a more complete understanding of the embodiments of the present invention and its advantages, reference should be made to the following description taken in conjunction with the drawings. It should be emphasized that the various features are not drawn to scale, but are for illustrative purposes only. The contents of the associated drawings are described as follows:

[0027] Please refer to FIG. 1, which is a cross-sectional schematic diagram showing a multilayer ceramic capacitor according to some embodiments of the present invention. The multilayer ceramic capacitor 100 of the present invention includes a multilayer ceramic body 110 and two end electrodes 120 provided on both ends of the multilayer ceramic body 110. The multilayer ceramic body 110 includes a plurality of internal electrode layers 111 and a plurality of ceramic dielectric layers 113 arranged alternately, with a portion of each internal electrode layer 111 electrically connected to one of the end electrodes 120 and the remaining portion electrically connected to the other of the end electrodes 120. As a result, the multilayer ceramic capacitor 100 of the present invention has a high capacitance value and favorable operability, and can meet the application requirements of high-end products. Furthermore, the multilayer ceramic capacitor 100 of the present invention has an internal electrode continuity of 85% or more, further improving its reliability.

[0028] Please refer to FIG. 2, a flowchart illustrating a method for manufacturing a multilayer ceramic capacitor 100 according to some embodiments of the present invention, together with FIG. 1. In the method 200, a plurality of internal electrode layers 111 are first formed, and a plurality of ceramic dielectric layers 113 are then formed, as shown in operations 210 and 220. As can be understood, the order in which the internal electrode layers 111 and the ceramic dielectric layers 113 are formed is not particularly limited, and the formation of both may be performed simultaneously. In other words, the execution of operations 210 and 220 is not limited to the order shown in FIG. 2, and operation 220 may be performed before operation 210, or operations 210 and 220 may be performed simultaneously.

[0029] In operation 210, the internal electrode layers 111 are fabricated from a plurality of metal particles, each including a nickel metal core and a metal oxide layer, where the metal oxide layer completely covers the nickel metal core. The metal particles for forming the internal electrode layers 111 may be made by the following method.

[0030] First, nickel metal particles are dispersed in a solvent to form a nickel-containing solution. Then, an atomization process is performed on the nickel-containing solution to atomize the solvent in the nickel-containing solution, coating the nickel metal particles with the atomized solvent and using the atomized solvent as a carrier for the nickel metal particles. The atomization solvent is not particularly limited as long as it can be successfully atomized and effectively removed in the subsequent film formation process. In some embodiments, based on the film formation process described below, the solvent may or may not contain a compound for forming a metal oxide layer, where the compound has metal atoms corresponding to the metal oxide layer. For example, the solvent may include, but is not limited to, n-butyl acetate, ethanol, other suitable solvents, or any combination thereof, and may or may not contain a compound for forming a metal oxide layer. In some embodiments, the atomization process may be performed using an ultrasonic atomizer, other devices capable of atomizing solvents, or any combination thereof. In some embodiments, the particle size of the nickel metal particles may be 100 nm to 200 nm, preferably 120 nm to 180 nm. When the particle size of the nickel metal particles is within the aforementioned range, the metal oxide layer formed in the subsequent film formation process can better cover the nickel metal particles, which helps to improve the internal electrode continuity of the formed internal electrode layer 111.

[0031] In some embodiments, an additional gas may be optionally used as a carrier gas to facilitate the movement of the nickel metal particles coated with the atomizing solvent. In these embodiments, the gas used as the carrier gas may be a pure substance or a mixed gas. The gas is not particularly limited as long as it can carry the nickel metal particles coated with the atomizing solvent and does not react with them. In some embodiments, the gas may include, but is not limited to, nitrogen, oxygen, argon, other suitable gases, or any combination thereof.

[0032] After the atomization process described above, the nickel metal particles coated with the atomization solvent are introduced into a reactor to carry out a deposition process to form a metal oxide layer coating the nickel metal cores.

[0033] When a film-forming process is performed and the solvent contains a compound for forming a metal oxide layer, an elevated temperature can be applied to the reactor to react the compound to form a metal oxide layer that coats the nickel metal particles, and other components in the solvent can be removed. When a film-forming process is performed and the solvent does not contain a compound for forming a metal oxide layer, an elevated temperature can be applied to the reactor to first remove the solvent, and then a compound for forming a metal oxide layer can be introduced into the reactor and react to form a metal oxide layer on the surface of the nickel metal particles. In some embodiments, the metal oxide layer can include tin oxide (e.g., SnO or SnO), other suitable metal oxides, or any combination thereof. For example, when the metal oxide layer includes tin oxide, the corresponding compound can include tetramethyl tin (TMT), tin tetrachloride hydrate (e.g., tin tetrachloride hydrate (SnCl·5H O)), other suitable tin-containing compounds, or any combination thereof. In some embodiments, the thickness of the metal oxide layer may be 1 nm to 50 nm, preferably 15 nm to 30 nm. When the thickness of the metal oxide layer is in the above range, the subsequently formed internal electrode layer 111 can have a low shrinkage rate during the sintering process, which contributes to improving the flatness thereof and further improving the internal electrode continuity of the internal electrode layer 111.

[0034] After forming the metal oxide layer, a magnetic separation process can be carried out to obtain metal particles for forming the internal electrode layer 111. The obtained metal particles are further mixed with an adhesive (binder, for example, a polyvinyl butyral adhesive) and an organic solvent (for example, ethanol) by ball milling and shaped to obtain the internal electrode layer 111.

[0035] 1 and 2. In operation 220, the method for manufacturing the ceramic dielectric layer 113 of the present invention is not particularly limited, and the ceramic dielectric layer 113 may be manufactured using methods and manufacturing processes known to those skilled in the art. For example, the ceramic dielectric layer 113 may be manufactured using the following flow: BaCO3 and TiO2 are weighed as perovskite raw materials containing Ba and Ti. Then, ball milling and heat treatment are performed to obtain barium titanate-based perovskite powder, which is the main component of the ceramic dielectric layer 113. Next, powders such as Dy2O3, YO3, MgO, MnO, and SiO, as well as the barium titanate-based perovskite powder, are ball milled. After uniformly mixing and drying, the raw material powder for the ceramic dielectric layer 113 is obtained. Thereafter, the raw material powder and an organic solvent (e.g., ethanol) are ball milled to obtain raw material slurry, which is then formed using a scraper to obtain a green sheet of the ceramic dielectric layer 113 having a thickness of 0.8 μm to 4 μm. Preferably, the thickness of the ceramic dielectric layer 113 may be 0.8 μm to 1.5 μm. For example, the thickness of the ceramic dielectric layer 113 may be approximately 0.8 μm.

[0036] After the internal electrode layers 111 and the ceramic dielectric layers 113 are formed, a lamination process is performed by alternately stacking the internal electrode layers 111 and the ceramic dielectric layers 113 to form a laminate, as shown in operation 230. During the lamination process, the manufactured internal electrode layers 111 and the ceramic dielectric layers 113 are alternately stacked, and one of the internal electrode layers 111 and the adjacent one extend in opposite directions. Here, due to the separation between the ceramic dielectric layers 113, two adjacent internal electrode layers 111 are electrically insulated.

[0037] After performing operation 230, the laminate is subjected to a sintering process 240 to form the laminated ceramic body 110. In the sintering process 240, a low-temperature combustion removal step is performed, followed by a high-temperature sintering step, as shown in operations 241 and 243. When performing the low-temperature combustion removal step, the adhesive and organic solvent in the internal electrode layers 111 and the ceramic dielectric layers 113 can be burned off. In some embodiments, the low-temperature combustion removal step is performed at a temperature of 280°C to 600°C, preferably 300°C to 500°C. It should be noted that when performing the low-temperature combustion removal step, the temperature is low and the sintering is performed in a nitrogen gas environment (oxygen partial pressure is about 10 -7MPa ~10 -9MPa ) the oxidized metal layer of the metal particles of the internal electrode layers 111 is not reduced and remains in an oxidized state.

[0038] The high-temperature sintering step is performed at a sintering temperature of 1000°C or higher and an oxygen partial pressure of 10 -10 The sintering is performed in an environment of 1000 psi or less. Due to the high temperature and low oxygen content, the metal oxide layer of the metal particles in the internal electrode layers 111 can be reduced to the corresponding metal atoms. Because the metal oxide layer completely covers the nickel metal particles, the metal atoms reduced by the high-temperature sintering step can also completely cover the nickel metal particles to form a nickel alloy. For example, if the metal oxide layer contains tin oxide, it can be reduced to metal tin by the high-temperature sintering step to form a nickel-tin alloy material together with the nickel metal particles. The reduction reaction induced by the high-temperature sintering step effectively reduces the shrinkage difference between the internal electrode layers 111 and the ceramic dielectric layers 113, effectively improves the internal electrode continuity of the multilayer ceramic body 110, and further improves the reliability and capacitance characteristics of the multilayer ceramic capacitor 100. In some embodiments, the temperature of the high-temperature sintering step is preferably 1120°C to 1180°C. To effectively enhance the reactivity of the reduction reaction, the high-temperature sintering step is preferably performed under an oxygen partial pressure of 100 psi. -12 MPa~10 -10If the reduction reaction of the metal oxide layer cannot be induced in the high-temperature sintering step, the metal particles coated with the metal oxide layer will increase the difference in shrinkage rate between the internal electrode layers 111 and the ceramic dielectric layers 113, which will significantly reduce the continuity of the internal electrodes of the multilayer ceramic body 110 and further reduce the reliability and capacitance characteristics of the multilayer ceramic capacitor 100.

[0039] In some embodiments, when a high-temperature sintering step is performed, in order to further improve the internal electrode continuity of the multilayer ceramic body 110, the high-temperature sintering step may first involve heating to the sintering temperature at a rate of 30°C / min or more and maintaining the sintering temperature for a certain period of time (e.g., 50 minutes or less). The sintering temperature is then cooled to room temperature at a rate of 10°C / min or more. The fast heating rate and short temperature maintenance time may further reduce the difference in shrinkage rate between the internal electrode layers 111 and the ceramic dielectric layers 113, thereby effectively improving the internal electrode continuity of the multilayer ceramic body 110. In some embodiments, the high-temperature sintering step preferably involves heating to the sintering temperature at a rate of 30°C / min to 100°C / min.

[0040] In some embodiments, before the high-temperature sintering step, in order to keep the nickel metal particles covered with the metal oxide layer, the metal particles of the internal electrode layer 111 are not treated in a reducing environment to prevent the metal oxide layer from being reduced to metal atoms. In some embodiments, the reducing environment is a temperature of 1000°C or higher and an oxygen content of 10 -10 MPa or less. That is, prior to the high temperature sintering step, the nickel metal particles are preferably treated or left in a low reducing environment. In some embodiments, the oxygen content of the low reducing environment is 10 -10 MPa~10 -12 The low reducing environment may have an oxygen content of 1000 MPa and a temperature of 1100° C. to 1200° C. When the oxygen content of the low reducing environment is within this range, not only can the metal oxide layer of the metal particles maintain its oxidized state, but also the nickel metal particles coated with the metal oxide layer are less likely to be oxidized, which allows the capacitance characteristics of the manufactured multilayer ceramic capacitor 100 to be maintained and contributes to improving the continuity of the internal electrodes.

[0041] 1 and 2. After the sintering process 240, as shown in operations 250 and 260, end electrodes 120 are formed on both ends of the multilayer ceramic body 110, respectively, to obtain the multilayer ceramic capacitor 100. The obtained multilayer ceramic capacitor 100 has an internal electrode continuity of 85% or more, and therefore has favorable capacitance characteristics and reliability.

[0042] The following application examples are used to illustrate the application of the present invention, but they are not intended to limit the present invention, and those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention.

[0043] Example 1

[0044] First, nickel metal particles with a particle size of 120 nm were dispersed in n-butyl acetate, and then, using an ultrasonic atomizer, nickel metal particles coated with atomized n-butyl acetate were formed. The atomized n-butyl acetate droplets were approximately several microns to several tens of microns in size, so they were able to completely coat the nickel metal particles. Next, a mixed gas of nitrogen gas and oxygen gas was introduced to act as a carrier for the nickel metal particles together with the atomized n-butyl acetate, and furthermore, a low-pressure (approximately 10 -1 The mixture gas was introduced into a reactor (200 psi, 10 ...

[0045] Please refer to Figures 3A and 3B, which show scanning electron micrographs and transmission electron micrographs, respectively, of the metal particles according to Example 1 of the present invention. According to Figures 3A and 3B, the nickel metal particles were coated with a tin oxide layer, the thickness of which was about 10 nm.

[0046] Next, the internal electrode layers of Example 1 were manufactured using metal particles by the above-mentioned method, and the ceramic dielectric layers of Example 1 were manufactured. A lamination process was carried out to obtain the laminate of Example 1. Next, the laminate was heated to 350°C in a nitrogen gas environment to burn off the adhesive, and then the atmosphere was changed to an oxygen partial pressure of 10 -10 MPa~10 -12 The environment was adjusted to a reduced pressure of 100 MPa, and the laminate was heated at a rate of 20° C. / min to 1200° C. After maintaining the temperature for 20 minutes, a laminated ceramic body of Example 1 was obtained.

[0047] Thereafter, end electrodes are formed on both ends of the multilayer ceramic body of Example 1 to form the multilayer ceramic capacitor of Example 1. The internal electrode continuity is evaluated by the following evaluation method, and the results are described later.

[0048] Example 2

[0049] First, 10 weight percent nickel metal particles were dispersed in water using a surfactant, and an ethanol solution of tin tetrachloride hydrate (SnCl4·5H2O) (concentration: 0.2 mole / L) was added. Next, an ultrasonic atomizer was used to form nickel metal particles coated with atomized droplets. Next, a mixture of nitrogen gas and argon gas was introduced to act as a carrier for the nickel metal particles together with the atomized n-butyl acetate. Then, the mixture was heated at low pressure (approximately 10 -1 The nickel metal particles were introduced into a reactor (pressure: 0.05 torr). In the reactor, a tin oxide layer was formed on the surface of the nickel metal particles by a hydrothermal method, yielding the metal particles of Example 2. The metal particles of Example 2 were then collected by an electromagnetic filter.

[0050] Reference was made to Figure 4, which shows a transmission electron microscope photograph of the metal particles according to Example 2 of the present invention. According to Figure 4, the thickness of the tin oxide layer on the metal particles was about 10 nm.

[0051] Next, a multilayer ceramic capacitor of Example 2 was manufactured by the same manufacturing method as that of Example 1, and the evaluation results of the internal electrode continuity thereof will be described later.

[0052] Comparative Example 1 and Comparative Example 2

[0053] Comparative Examples 1 and 2 were manufactured using the same manufacturing method as the multilayer ceramic capacitor of Example 1, but differed in that the internal electrode layers of the multilayer ceramic capacitors of Comparative Examples 1 and 2 were manufactured using nickel metal particles not coated with a tin oxide layer in Examples 1 and 2, and by mixing barium titanate with a particle size of 30 nm (containing 5 weight percent nickel metal particles), and the evaluation results of the internal electrode continuity will be described later.

[0054] Evaluation method for internal electrode continuity

[0055] The internal electrode continuity of the above-mentioned Examples 1 and 2 and Comparative Examples 1 and 2 is calculated using the following formula based on high-magnification optical microscope photographs of the multilayer ceramic body. JPEG0007739357000001.jpg15153

[0056] where L t represents the total length of each internal electrode layer. dc is L t The internal electrode continuity of the present invention represents the sum of the lengths of discontinuous portions (for example, discontinuous portions that shrink due to high-temperature sintering) in the internal electrode layers, with respect to the internal electrode continuity. The internal electrode continuity of the present invention is evaluated as the average value of the internal electrode continuity of all the internal electrode layers in the multilayer ceramic capacitor.

[0057] See FIGS. 5A-5D, which are optical microscope photographs showing cross sections of multilayer ceramic bodies of multilayer ceramic capacitors according to Examples 1 and 2 of the present invention at high magnification. Compared to Comparative Examples 1 and 2 (FIGS. 5C and 5D), the internal electrode layers of the multilayer ceramic capacitors according to Examples 1 and 2 (FIGS. 5A and 5B) have fewer discontinuous portions and therefore have favorable internal electrode continuity. According to the aforementioned internal electrode continuity evaluation method, the internal electrode continuities of the multilayer ceramic capacitors according to Examples 1 and 2, Comparative Examples 1 and 2, were 95%, 93%, 81%, and 79%, respectively. Thus, the multilayer ceramic capacitors according to the present invention have internal electrode continuity of 85% or more, which effectively improves the capacitance characteristics and reliability of the multilayer ceramic capacitor and further meets the application requirements of high-end products.

[0058] Please refer to Figures 6A, 6B, 7A, and 7B. Figures 6A and 7A show scanning transmission electron microscopy (STEM) photographs of the multilayer ceramic bodies of the multilayer ceramic capacitors according to Example 1 and Comparative Example 1 of the present invention, respectively. Figures 6B and 7B show spatially resolved electron energy loss spectroscopy (SR-EELS) photographs of Figures 6A and 7A, respectively.

[0059] FIGS. 6A and 7A show the interfaces between the internal electrode layers and the ceramic dielectric layers in the multilayer ceramic bodies of Example 1 and Comparative Example 1, respectively. To further analyze the crystalline properties of the internal electrode layers and the ceramic dielectric layers, spatially resolved electron energy loss spectroscopy was performed on the dashed-line frames in FIGS. 6A and 7A, and the results are shown in FIGS. 6B and 7B, respectively. In FIGS. 6B and 7B, the left-hand images correspond to the dashed-line frames in FIGS. 6A and 7A (i.e., the positions corresponding to the slits in the SR-EELS analysis), and the dashed lines in the left-hand images represent the interfaces between the internal electrode layers (upper layers) and the ceramic dielectric layers (lower layers). In FIGS. 6B and 7B, the right-hand images are the analysis results from the SR-EELS analysis.

[0060] The SR-EELS analysis images were further divided into five regions, regions A1 to A5 and regions B1 to B5 in Figures 6B and 7B, respectively. Regions A5 and B5 are adjacent to the interfaces between the internal electrode layers and the ceramic dielectric layers. According to the results of the images in Figures 6B and 7B, the image analysis of regions A5 and B5 differs. To understand the differences between regions A5 and B5, we further analyzed the electron energy loss near-edge measures (ELNES) of regions A1 to A5 and regions B1 to B5 in Figures 6B and 7B, and the results are shown in Figures 8A and 8B, respectively.

[0061] 8A and 8B, regions A1 and A2 and regions B1 to B5 all have four split signal peaks, while regions A3 to A5 have only two signal peaks. This change in the spectrum is due to oxygen vacancies formed in the ceramic dielectric layer, which cause titanium atoms in the ceramic dielectric layer to gain electrons, resulting in the formation of Ti 4+ Ti 3+ The barium titanate adjacent to the interface between the ceramic dielectric layer and the internal electrode layer becomes a semiconductor that realizes electron hopping conduction of titanium atoms. This allows the ceramic dielectric layer adjacent to the interface to form oxygen vacancies, resulting in the formation of Ti 4+ Ti3+ Therefore, in the present invention, a Schottky barrier can be formed at the interface between the internal electrode layer made of specific nickel alloy particles and the ceramic dielectric layer, thereby suppressing leakage current of the multilayer ceramic capacitor. In some embodiments, the thickness of the oxygen vacancy in the ceramic dielectric layer may be 10 nm to 100 nm, calculated from the interface between the internal electrode layer and the ceramic dielectric layer.

[0062] As a result, the present invention provides an interface between the internal electrode layer and the ceramic dielectric layer with good flatness, and specific nickel alloy particles in the internal electrode layer contribute to the formation of a Schottky barrier at this interface, thereby improving the long-term reliability of the multilayer ceramic capacitor and further contributing to improving the reliability of the multilayer ceramic capacitor.

[0063]

[0006] Therefore, since the internal electrode layers of the present invention are manufactured using specific nickel alloy particles, the difference in shrinkage between the internal electrode layers and the ceramic dielectric layers can be reduced, and the internal electrode continuity of the internal electrode layers of the multilayer ceramic capacitor can be improved, resulting in effective improvements in the capacitance characteristics and reliability of the multilayer ceramic capacitor. The nickel alloy particles used here first coat the surfaces of the nickel metal particles with a metal oxide layer, and then the high-temperature sintering step of the sintering process reduces the metal oxide layer to a metal layer, thereby reducing the difference in shrinkage between the internal electrode layers and the ceramic dielectric layers. Furthermore, the internal electrode layers of the present invention help form oxygen vacancies in the ceramic dielectric layers, which causes electron hopping conduction in the material in the ceramic dielectric layers and forms semiconductor regions. This allows a Schottky barrier to be formed at the interface between the internal electrode layers of the present invention and the ceramic dielectric layers, further suppressing leakage current and improving the interfacial flatness and the long-term reliability of the multilayer ceramic capacitor.

[0064] Although the present invention has been disclosed as above by way of embodiments, it is not limited thereto, and those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention is determined by the content specified in the following claims. [Explanation of symbols]

[0065] 100 Multilayer ceramic capacitors 110 Laminated ceramic body 111 Internal electrode layer 113 Ceramic dielectric layer 120 End electrode 200 ways 210, 220, 230, 241, 243, 250, 260 operations 240 Sintering Process A1, A2, A3, A4, A5 area B1, B2, B3, B4, B5 area

Claims

1. forming a plurality of internal electrode layers each made of a plurality of metal particles including a nickel metal core and a metal oxide layer completely covering the nickel metal core; forming a plurality of ceramic dielectric layers; a step of alternately stacking the internal electrode layers and the ceramic dielectric layers to form a laminate; subjecting the laminate to a sintering process to form a laminated ceramic body; forming end electrodes on both ends of the multilayer ceramic body to obtain a multilayer ceramic capacitor; Equipped with the sintering process includes a low-temperature burning-off step and a high-temperature sintering step, and when the high-temperature sintering step is performed, the metal oxide layer of each of the metal particles is reduced to a metal layer; the metal oxide layer has a thickness of 1 nm to 50 nm; The oxygen partial pressure in the high-temperature sintering step is 10 －１２ MPa to 10 －１０ MPa, The multilayer ceramic capacitor has an internal electrode continuity of 85% or more, the metal oxide layer comprises tin oxide and the metal layer comprises metallic tin; When the high-temperature sintering step is performed, oxygen vacancies are formed in each of the ceramic dielectric layers, and the oxygen vacancies are adjacent only to interfaces between each of the ceramic dielectric layers and each of the internal electrode layers; The interface forms a Schottky barrier. A method for manufacturing a multilayer ceramic capacitor.

2. The method for forming the metal particles includes: the atomized solution being the carrier for the nickel metal core; performing a film-forming process on the atomized solution containing the nickel metal core to form the metal oxide layer; After forming the metal oxide layer, a magnetic separation process is performed to obtain the metal particles; The method for producing a multilayer ceramic capacitor according to claim 1 , comprising:

3. The method for manufacturing a multilayer ceramic capacitor according to claim 2 , wherein the atomized solution contains a compound having a metal atom corresponding to the metal oxide layer.

4. The method for manufacturing a multilayer ceramic capacitor according to claim 1 , wherein the internal electrode layers are not treated in a reducing environment before the high-temperature sintering step.

5. The oxygen partial pressure of the reducing environment is 10 －１０ 5. The method for producing a multilayer ceramic capacitor according to claim 4, wherein the pressure is 0.01 MPa or less.

6. 5. The method for producing a multilayer ceramic capacitor according to claim 4, wherein the temperature of the reducing environment is 1000° C. or higher.

7. The high-temperature sintering step performing a heating step with a heating rate of 30°C / min or more; performing a temperature maintenance step in which the temperature maintenance time is 50 minutes or less; performing a cooling step at a cooling rate of 10°C / min or more; The method for producing a multilayer ceramic capacitor according to claim 1 , comprising:

8. 2. The method for producing a multilayer ceramic capacitor according to claim 1, wherein the thickness of the oxygen vacancy in each of the ceramic dielectric layers is 10 nm to 100 nm when calculated from the interface.

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