Dielectric ceramic material, method for manufacturing the same, and multilayer ceramic capacitor

Abstract

The present invention relates to a dielectric ceramic material, a manufacturing method thereof, and a multilayer ceramic capacitor. By means of barium titanate particles with a specific average particle size, a grinding treatment with a specific number of grinding times, and a dopant with a specific composition, the manufacturing method of the dielectric ceramic material can manufacture a dielectric ceramic material including grains with a core-shell structure. A specific volume fraction of the shell layer within the grains can improve the capacitance temperature coefficient of the dielectric ceramic material between -55°C and 150°C, thereby enhancing the high-temperature thermal stability of the manufactured multilayer ceramic capacitor and improving its life performance.

Description

Technical Field

[0001] The present invention relates to a dielectric ceramic material, a method for manufacturing the same, and a multilayer ceramic capacitor, and particularly to a dielectric ceramic material having high-temperature thermal stability and good life performance, a method for manufacturing the same, and a multilayer ceramic capacitor. Background Art

[0002] Recently, multilayer ceramic capacitors (MLCCs) have been developing towards miniaturization, multifunctionality, and high capacitance to meet the miniaturization and lightweight requirements of electronic devices. Moreover, multilayer ceramic capacitors often operate in high-temperature environments. For example, in the automotive industry, multilayer ceramic capacitors are integrated into the electronic components in the engine compartment. Therefore, multilayer ceramic capacitors must have high-temperature thermal stability and good life performance. The Electronic Industries Association (EIA) has established the X8R specification for high-temperature capacitors for safety considerations. That is, within the operating temperature range of -55°C to 150°C, with the capacitance measured at 25°C as the reference, the maximum capacitance change is not more than 15%.

[0003] The prior art uses barium titanate as the main component and dopes oxides such as zirconium, barium, manganese, and silicon to manufacture dielectric ceramic materials. The multilayer ceramic capacitors made therefrom cannot have both high-temperature thermal stability and good life performance, and their thickness cannot be less than 5 μm, so they cannot be applied to miniaturized and lightweight electronic devices.

[0004] In view of this, there is an urgent need to develop a new dielectric ceramic material and a method for manufacturing the same to improve the above-mentioned disadvantages of multilayer ceramic capacitors. Summary of the Invention

[0005] In view of the above problems, one aspect of the present invention is to provide a method for manufacturing a dielectric ceramic material. This manufacturing method uses barium titanate particles with a specific average particle size, a dopant with a specific composition, and a grinding treatment with a specific number of grinding times to manufacture a dielectric ceramic material containing a plurality of grains, and each grain has a shell layer with a specific volume fraction. This shell layer can improve the capacitance temperature coefficient of the dielectric ceramic material between -55°C and 150°C, thereby enhancing the high-temperature thermal stability of the manufactured multilayer ceramic capacitor and improving its life performance.

[0006] Another aspect of the present invention is to provide a dielectric ceramic material. This dielectric ceramic material is obtained by using the aforementioned method for manufacturing a dielectric ceramic material.

[0007] Another aspect of the present invention is to provide a multilayer ceramic capacitor. This multilayer ceramic capacitor includes a stacked structure, and the dielectric ceramic layers of this stacked structure are formed of the aforementioned dielectric ceramic material.

[0008] According to one aspect of the present invention, a manufacturing method of a dielectric ceramic material is provided. In this manufacturing method, barium titanate particles and a dopant are provided, wherein the dopant includes ytterbium oxide, silicon dioxide, manganese carbonate, barium carbonate, and vanadium pentoxide. The average particle size of the barium titanate particles is greater than 0.15 μm and not greater than 0.45 μm, and based on the amount of the barium titanate particles being 100 mole percentages, the amount of ytterbium oxide is greater than 0 mole percentages and not greater than 3.2 mole percentages. Then, the barium titanate particles, the dopant, and a dispersant are mixed and subjected to a grinding process to obtain a powder mixture, wherein the number of grinding times of the grinding process is 5 to 9 times. Then, a binder is added to the powder mixture and a forming process is performed to obtain a sheet. The sheet is then subjected to a sintering process to obtain the dielectric ceramic material, wherein the sintering temperature of the sintering process is 1200 °C to 1420 °C, and the sintering time of the sintering process is 0.5 hour to 4.5 hours.

[0009] According to an embodiment of the present invention, based on the amount of the barium titanate particles being 100 mole percentages, the amount of silicon dioxide is greater than 0.9 mole percentages and not greater than 3.8 mole percentages, the amount of vanadium pentoxide is 0.05 mole percentages to 1.0 mole percentages, the amount of manganese carbonate is 0.10 mole percentages to 0.35 mole percentages, and the amount of barium carbonate is 1.0 mole percentages to 4.0 mole percentages.

[0010] According to another embodiment of the present invention, the dopant optionally includes dysprosium oxide, and based on the amount of the barium titanate particles being 100 mole percentages, the amount of dysprosium oxide is less than 1.86 mole percentages.

[0011] According to still another embodiment of the present invention, the dopant optionally includes at least one of the group consisting of magnesium carbonate, yttrium oxide, calcium zirconium trioxide, and calcium carbonate.

[0012] According to yet another embodiment of the present invention, based on the amount of the barium titanate particles being 100 mole percentages, the amount of the dopant is 5 mole percentages to 20 mole percentages.

[0013] According to yet another embodiment of the present invention, the grinding speed of the grinding process is 5 m / s to 15 m / s.

[0014] According to yet another embodiment of the present invention, the atmosphere of the sintering process includes 0.5% to 3.5% hydrogen.

[0015] According to another aspect of the present invention, a dielectric ceramic material is provided. This dielectric ceramic material is obtained by using the manufacturing method of the aforementioned dielectric ceramic material. The dielectric ceramic material includes a plurality of grains, and each grain includes a core and a shell layer, wherein the average particle size of each grain is from 0.15 μm to 0.25 μm, and based on the volume of each grain being 100 volume fractions, the volume of the core is from 40 volume fractions to 75 volume fractions, and the volume of the shell layer is from 25 volume fractions to 60 volume fractions.

[0016] According to an embodiment of the present invention, the capacitance temperature coefficients of the dielectric ceramic material at -55 °C and 150 °C are both not greater than 15%.

[0017] According to still another aspect of the present invention, a multilayer ceramic capacitor is provided. This multilayer ceramic capacitor includes a stacked structure and two external electrodes. This stacked structure includes a plurality of dielectric ceramic layers and a plurality of internal electrode layers. These dielectric ceramic layers are formed from the aforementioned dielectric ceramic material, wherein these dielectric ceramic layers are stacked in sequence. These internal electrode layers are respectively disposed between every two adjacent ones of these dielectric ceramic layers, and alternately protrude from the opposite first end face and second end face of the stacked structure in sequence. The two external electrodes are respectively disposed on the first end face and the second end face, and are respectively electrically connected to these internal electrode layers protruding from the first end face or the second end face.

[0018] By applying the manufacturing method of the dielectric ceramic material of the present invention, wherein by using barium titanate particles with a specific average particle size, a dopant with a specific composition, and a grinding treatment with a specific number of grinding times, the manufacturing method of the dielectric ceramic material can manufacture a dielectric ceramic material including a plurality of grains, and the shell layer with a specific volume fraction of each grain can improve the capacitance temperature coefficient of the dielectric ceramic material between -55 °C and 150 °C, thereby enhancing the high-temperature thermal stability of the manufactured multilayer ceramic capacitor and improving its life performance. Description of the Drawings

[0019] To have a more complete understanding of the embodiments of the present invention and their advantages, please now refer to the following description and cooperate with the corresponding drawings. It must be emphasized that the various features are not drawn to scale and are only for illustrative purposes. The description of the relevant drawings is as follows:

[0020] Figure 1 A flowchart showing the manufacturing method of the dielectric ceramic material according to an embodiment of the present invention is depicted.

[0021] Figure 2 A schematic structural diagram showing the dielectric ceramic material according to an embodiment of the present invention is depicted.

[0022] Figure 3 A schematic structural diagram showing the multilayer ceramic capacitor according to an application example of the present invention is depicted. Detailed Description of the Embodiments

[0023] The manufacturing and use of the embodiments of the present invention are discussed in detail below. However, it can be understood that the embodiments provide many applicable inventive concepts that can be implemented in a variety of specific contexts. The specific embodiments discussed are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0024] The manufacturing method of the dielectric ceramic material of the present invention uses barium titanate particles with an average particle size greater than 0.15 μm and not greater than 0.45 μm, a dopant with a specific composition, and a grinding treatment with 5 to 9 grinding times to manufacture a dielectric ceramic material containing a plurality of grains. The dopant includes manganese carbonate (MnCO 3 ), barium carbonate (BaCO 3 ), ytterbium oxide (Yb 2 O 3 ), vanadium pentoxide (V 2 O 5 ), and silicon dioxide (SiO 2 ). Based on the usage amount of barium titanate particles being 100 mole percentages, the usage amount of ytterbium oxide is greater than 0.0 mole percentage and not greater than 3.2 mole percentages. These grains have a core-shell structure (i.e., a core and a shell), and the volume of the shell is 25 volume fractions to 75 volume fractions. This shell can slow down the drastic change in capacitance of the barium titanate grains in the core caused by temperature changes. Therefore, the shell can improve the capacitance temperature coefficient of the dielectric ceramic material between -55°C and 150°C, thereby enhancing its high-temperature thermal stability and improving its life performance while maintaining the basic electrical properties of the multilayer ceramic capacitor.

[0025] The "thermal stability" referred to in the present invention is evaluated by calculating the maximum change amount (i.e., the capacitance temperature coefficient described later) of the capacitance values measured at -55°C and 150°C based on the capacitance value of the multilayer ceramic capacitor measured at 25°C. When the maximum change amounts at -55°C and 150°C are both not greater than 15%, the multilayer ceramic capacitor has high thermal stability, that is, it has both low-temperature (-55°C) thermal stability and high-temperature (150°C) thermal stability.

[0026] The "life performance" referred to in the present invention measures the time-course change of the insulation resistance value of the multilayer ceramic capacitor at 180°C. The time when the insulation resistance value reaches one-tenth of the initial measured value is used as the insulation failure time of the multilayer ceramic capacitor, and 15 samples are statistically analyzed to obtain the average failure time. The life performance of the multilayer ceramic capacitor is evaluated using the average failure time. The detailed evaluation method is as described in the average failure time test later. When the average failure time is greater than 10 hours, the multilayer ceramic capacitor has good life performance.

[0027] As used herein, the "basic electrical properties" of the invention refer to the capacitance, dielectric loss, insulation resistance, and breakdown voltage of a multilayer ceramic capacitor, and the appropriate ranges thereof are a capacitance greater than 40 nF, a dielectric loss less than 2.5%, an insulation resistance of 1×10 9 Ω to 20×10 9 Ω, and a breakdown voltage greater than 450 V. When the basic electrical properties of the multilayer ceramic capacitor are maintained within the appropriate ranges, it can be applied to miniaturized and lightweight electronic devices.

[0028] Please refer to Figure 1 , in the manufacturing method 100 of the dielectric ceramic material, barium titanate (BaTiO 3 ) particles and dopants are first provided, as shown in operation 110. The barium titanate particles serve as the main component. If the manufacturing method 100 does not use barium titanate particles but uses other salts containing a perovskite structure, the dielectric constant of the dielectric ceramic material will be significantly reduced, and the cost of production raw materials will be increased.

[0029] The average particle size of the barium titanate particles is greater than 0.15 μm and not greater than 0.45 μm. If the average particle size of the barium titanate particles is not greater than 0.15 μm, the dielectric constant of the dielectric ceramic material is likely to be lower than 1400, which is not conducive to the miniaturization and high capacitance value of the multilayer ceramic capacitor. If the average particle size of the barium titanate particles is greater than 0.45 μm, the number of grains contained in the single-layer dielectric layer produced is less, so the life performance of the produced multilayer ceramic capacitor is reduced. Preferably, the average particle size of the barium titanate particles is 0.20 μm to 0.40 μm.

[0030] In some embodiments, the barium titanate particles can be manufactured by the oxalic acid method, the solid-phase method, or the hydrothermal method. In some specific examples, the oxalic acid method is to obtain barium oxalate titanate (BaTiO(C 2 O 4 ) 2 ·4H 2 O) by mixing titanium chloride, barium chloride, water, and oxalic acid, where the highest synthesis temperature only needs to be in the range of 600°C to 700°C, and the content ratio of barium to titanium in the barium titanate particles can be controlled by the process, which is conducive to the diffusion of dopants into the barium titanate particles.

[0031] The dopants include ytterbium oxide (Yb 2 O 3 ), silicon dioxide (SiO 2 ), manganese carbonate (MnCO 3 ), barium carbonate (BaCO 3 ), and vanadium pentoxide (V 2 O 5) If the dopant does not contain the aforementioned composition, the influence of the shell layer of the grains of the prepared dielectric ceramic material on the phase transition temperature of the core barium titanate is reduced, and the capacitance temperature coefficient of the prepared multilayer ceramic capacitor cannot be effectively improved, thus reducing its life performance.

[0032] Based on the amount of barium titanate particles being 100 mole percent, the amount of ytterbium oxide is greater than 0 mole percent and not greater than 3.2 mole percent. If the amount of ytterbium oxide is greater than 3.2 mole percent, the capacitance temperature coefficient of the dielectric ceramic material is increased, thus reducing the thermal stability of the multilayer ceramic capacitor. Preferably, the amount of ytterbium oxide is from 0.6 mole percent to 3.0 mole percent.

[0033] Based on the amount of barium titanate particles being 100 mole percent, the amount of silicon dioxide is greater than 0.9 mole percent and not greater than 3.8 mole percent. When the amount of silicon dioxide is within the aforementioned range, the capacitance temperature coefficient of the dielectric ceramic material is improved, thus enhancing the thermal stability of the multilayer ceramic capacitor. Preferably, the amount of silicon dioxide is from 1.8 mole percent to 3.6 mole percent.

[0034] In some specific examples, based on the amount of barium titanate particles being 100 mole percent, the amount of manganese carbonate is from 0.10 mole percent to 0.35 mole percent. Based on the amount of barium titanate particles being 100 mole percent, the amount of barium carbonate is from 1.0 mole percent to 4.0 mole percent. Based on the amount of barium titanate particles being 100 mole percent, the amount of vanadium pentoxide is from 0.05 mole percent to 1.0 mole percent. When the amounts of manganese carbonate, barium carbonate and / or barium carbonate are within the aforementioned ranges, the grains of the prepared dielectric ceramic material have a core-shell structure, thus improving the thermal stability and life performance of the multilayer ceramic capacitor.

[0035] In addition, the dopant may optionally contain dysprosium oxide (Dy 2 O 3 ), and based on the amount of barium titanate particles being 100 mole percent, the amount of dysprosium oxide is less than 1.86 mole percent. When the amount of dysprosium oxide is within the aforementioned range, the dielectric constant of the dielectric ceramic material is increased, and the capacitance temperature coefficient of the dielectric ceramic material at -55 °C is improved, thereby enhancing the thermal stability of the multilayer ceramic capacitor. Preferably, the mole number of dysprosium oxide is not greater than 0.65 mole percent.

[0036] In addition, the dopant may selectively include at least one of the group consisting of magnesium carbonate, yttrium oxide, calcium zirconium trioxide, and calcium carbonate. That is to say, based on the amount of barium titanate particles being 100 mole percentages, the amount of yttrium oxide is less than 3.2 mole percentages. When the amount of yttrium oxide is within the aforementioned range, the thermal stability of the multilayer ceramic capacitor can be improved, and the capacitance of the fabricated multilayer ceramic capacitor can be increased. In addition, based on the amount of barium titanate particles being 100 mole percentages, the amounts of magnesium carbonate, calcium zirconium trioxide, and calcium carbonate are respectively less than 2.2 mole percentages, not more than 4.0 mole percentages, and less than 2.2 mole percentages. When the amounts of magnesium carbonate, calcium zirconium trioxide, and / or calcium carbonate are within the aforementioned ranges, it is beneficial for the grains of the fabricated dielectric ceramic material to have a core-shell structure, thus improving the thermal stability and life performance of the multilayer ceramic capacitor.

[0037] In some embodiments, based on the amount of barium titanate particles being 100 mole percentages, the amount of the dopant is 5 mole percentages to 20 mole percentages. When the amount of the dopant is within the aforementioned range, the shell layer in the dielectric ceramic material grains formed by the dopant can affect the phase transition temperature of the core barium titanate and enhance the withstand voltage reliability, thus improving the thermal stability and life performance of the multilayer ceramic capacitor. Preferably, the mole number of the dopant is 9.4 mole percentages to 14.4 mole percentages.

[0038] In some specific examples, the molar ratio of yttrium oxide to ytterbium oxide can be 0.2 to 8, and preferably can be 0.2 to 0.3. When the molar ratio of yttrium oxide to ytterbium oxide is within the aforementioned range, the thermal stability and life performance of the multilayer ceramic capacitor can be improved. In some embodiments, salts containing terbium (Tb) and holmium (Ho) are not used as the dopant, and the fabricated multilayer ceramic capacitor has thermal stability and good life performance.

[0039] After operation 110, barium titanate particles, the dopant, and a dispersant are mixed and subjected to a grinding process to obtain a powder mixture, as shown in operation 120. The dispersant is used to disperse the components of the dielectric ceramic material (i.e., barium titanate particles, the dopant, and other components). The dispersant of the present invention is not particularly limited, as long as the aforementioned dispersion purpose is achieved. In some embodiments, the dispersant may include polyethylene oxide resins and other resins. In some specific examples, based on the amount of barium titanate particles being 100 weight percentages, the amount of the dispersant can be 0.5 weight percentages to 5 weight percentages.

[0040] During the grinding process, dopants can be doped onto the surface of barium titanate particles via the pressure applied during grinding. As the number of grinding times increases, more dopants are doped onto the surface of barium titanate particles to form a shell doped with dopants on the surface of barium titanate particles. The undoped part inside the barium titanate particles is called the core, and the combination of the core and the aforementioned shell is the grain of the electro-ceramic material.

[0041] The number of grinding times for the grinding process is 5 to 9 times. If the number of grinding times is less than 5 times, the shell is too thin, reducing the influence of the shell on the core, so the temperature coefficient of capacitance of the dielectric ceramic material cannot be effectively improved, the thermal stability of the multilayer ceramic capacitor is reduced, and its life performance is reduced. If the number of grinding times is greater than 9 times, the too thick shell reduces the dielectric constant of the dielectric ceramic material and the capacitance of the multilayer ceramic capacitor.

[0042] In some embodiments, the grinding process can be carried out using a bead mill, and the grinding beads can be zirconia balls with a diameter of 0.05 mm to 0.3 mm. Preferably, the grinding beads can be zirconia balls with a diameter of 0.1 mm. In some specific examples, the grinding speed of the bead mill can be 5 m / s to 15 m / s, and preferably 10 m / s. When the grinding speed is within the aforementioned range, the influence of the shell on the grains of the core is increased to reduce the capacitance variation of the overall grains caused by temperature changes, so the thermal stability of the multilayer ceramic capacitor is improved and its life performance is enhanced.

[0043] After operation 120, a binder is added to the powder mixture and a forming process is carried out to obtain a sheet, as shown in operation 130. The binder is used to bond the powder mixture to facilitate the formation of the sheet. The binder of the present invention is not particularly limited, as long as it serves the purpose of achieving the aforementioned bonding. In some embodiments, the binder can include polyvinyl acetal resins and other resins. In some specific examples, based on the amount of barium titanate particles being 100 weight percentages, the amount of the binder can be 5 weight percentages to 15 weight percentages.

[0044] After the binder is added to the powder mixture, the two are uniformly mixed to form a slurry. In some embodiments, a solvent can be selectively added to the powder mixture before, during, or after the addition of the binder to assist the binder in bonding the powder mixture. Specific examples of the solvent can include, but are not limited to, solvents such as water, alcohol, and / or toluene.

[0045] In some embodiments, the forming process may utilize a film such as polyethylene terephthalate (PET) or polyethylene (PE) as the substrate for carrying the slurry. For example, a doctor blade may be used to coat the slurry on the substrate to make the slurry present as a sheet, or after granulating the slurry, it may be pressed into a sheet by a tablet press. In some embodiments, the thickness of the sheet may be no more than 10 μm, and preferably may be 3 μm to 6 μm. When the thickness of the sheet is within the aforementioned range, it is beneficial for the miniaturization of the multilayer ceramic capacitor, so that the multilayer ceramic capacitor can be applied to miniaturized and lightweight electronic devices.

[0046] After operation 130, the sheet is subjected to a sintering process to obtain a dielectric ceramic material, as shown in operation 140. The sintering temperature of the sintering process is 1200 °C to 1420 °C, and the sintering time is 0.5 hour to 4.5 hours. Preferably, the sintering temperature is 1300 °C to 1320 °C, and the sintering time is 1 hour. If the sintering temperature is less than 1200 °C, too low a sintering temperature cannot generate a dielectric ceramic material, or residual organic substances (such as binders, dispersants, and / or solvents) remain in the ceramic material, deteriorating the capacitance temperature coefficient of the dielectric ceramic material, thus reducing the thermal stability of the multilayer ceramic capacitor and its life performance. If the sintering temperature is greater than 1420 °C, the grains of the fabricated dielectric ceramic material may not have a core-shell structure, deteriorating the capacitance temperature coefficient of the dielectric ceramic material, thus reducing the thermal stability of the multilayer ceramic capacitor and its life performance, or drastically reducing the dielectric constant of the multilayer ceramic capacitor.

[0047] In some embodiments, the atmosphere of the sintering process contains 0.5% to 3.5% hydrogen. When the sintering process uses the aforementioned atmosphere, it is easy to generate oxygen vacancies on the grain surface and facilitate the diffusion of dopants into the grains. In these embodiments, the gas contained in the atmosphere may include nitrogen and exclude oxygen.

[0048] Another aspect of the present invention is to provide a dielectric ceramic material prepared by the aforementioned manufacturing method. Please refer to Figure 2, the dielectric ceramic material 200 includes grains 210 and other regions 220 of the non-grain 210, and the grains 210 include a core 211 (the aforementioned undoped dopant portion located inside the barium titanate particles) and a shell 212 (the aforementioned portion doped with a dopant on the surface of the barium titanate particles). As mentioned above, the other regions 220 may be formed by dopants that are not doped to the surface of the barium titanate particles (i.e., formed by pure dopants), and / or may be composed of extremely small grains 210. The average particle size of the grains 210 is 0.15 μm to 0.25 μm. If the average particle size of the grains 210 is not within the aforementioned range, a dielectric ceramic layer with a thickness of not less than 5 μm cannot be obtained from the dielectric ceramic material, and the manufactured multilayer ceramic capacitor cannot be applied to miniaturized and lightweight electronic devices. Preferably, the average particle size of the grains 210 can be 0.18 μm to 0.20 μm, so that the thickness of the dielectric ceramic layer is not greater than 3.5 μm, and thus the multilayer ceramic capacitor can be applied to miniaturized and lightweight electronic devices.

[0049] Based on the volume of the grains 210 being 100 volume fractions, the volume of the core 211 is 40 volume fractions to 75 volume fractions, and the volume of the shell 212 is 25 volume fractions to 60 volume fractions. If the volumes of the core 211 and the shell 212 are not within the aforementioned range, the too-thin shell 212 reduces the thermal stability and life performance of the multilayer ceramic capacitor. The too-thick shell 212 reduces the dielectric constant of the dielectric ceramic material 200 and reduces the capacitance of the multilayer ceramic capacitor. Preferably, the volume ratio of the core 211 to the shell 212 can be 0.4 to 0.7.

[0050] In some application examples, based on the capacitance value measured for the dielectric ceramic material at 25 °C, the change amounts of the capacitance values measured for the dielectric ceramic material at -55 °C and 150 °C are both not greater than 15%. When the dielectric ceramic material has the aforementioned change amount of the capacitance value, the manufactured multilayer ceramic capacitor can meet the EIA X8R specification, and thus can be applied to electronic devices operating in a high-temperature environment. Preferably, the aforementioned change amounts of the capacitance values are both not greater than 10%.

[0051] Another aspect of the present invention is to provide a multilayer ceramic capacitor. Please refer to Figure 3, the multilayer ceramic capacitor 300 includes a stacked structure 310 and two external electrodes 320. The stacked structure 310 includes a plurality of dielectric ceramic layers 311 stacked in sequence, and a plurality of internal electrodes 312. These internal electrodes 312 are respectively disposed between every two adjacent ones of these dielectric ceramic layers 311, and alternately protrude from the opposite first end face 310A and second end face 310B of the stacked structure 310 in sequence. The dielectric ceramic layers 311 are made of the aforementioned dielectric ceramic material. In some application examples, the dielectric ceramic material is coated on a PET or PE film to form a sheet. A paste for forming the internal electrodes 312 is printed on the sheet, cut, stacked in sequence, and then the cut sheets are pressed together. Then, the pressed sheet is degreased and sintered to obtain the stacked structure 310, where the plurality of internal electrodes 312 are made of the paste of the aforementioned internal electrodes 312. The aforementioned processes of cutting, pressing, degreasing, and sintering can all be methods commonly used by those skilled in the technical field to which the present invention pertains.

[0052] Then, two external electrodes 320 are disposed on the first end face 310A and the second end face 310B of the stacked structure 310. The connection between the external electrodes 320 and the internal electrodes 312 is determined according to the positions where the external electrodes 320 are disposed, that is, the first end face 310A or the second end face 310B. For example, one external electrode 320 disposed on the first end face 310A is electrically connected to these internal electrode layers 312 protruding from the first end face 310A, and the other external electrode 320 disposed on the second end face 310B is electrically connected to these internal electrode layers 312 protruding from the second end face 310B. For example, the two external electrodes 320 can be disposed by electroplating. In these application examples, the two external electrodes 320 serve as the positive electrode and the negative electrode respectively to connect to an external power source. The materials of the internal electrodes 312 and the external electrodes 320 can be materials commonly used by those skilled in the technical field to which the present invention pertains. For example: copper, nickel, tin, and their alloys.

[0053] The following uses examples to illustrate the application of the present invention, but it is not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention.

[0054] Manufacture of Dielectric Ceramic Material

[0055] Example 1

[0056] The dielectric ceramic material of Example 1 is mixed with 100 mole percentages of barium titanate particles having an average particle size of 0.20 μm to 0.40 μm, 8.83 mole percentages of a dopant, and 1.2 weight percentages of a polyoxyalkylene resin, and 400 g of zirconia grinding balls (with a diameter of 2 mm) are used to grind at a rate of 238 rpm for 1 hour to obtain a powder mixture. Then, 5 weight percentages to 15 weight percentages of a polyvinyl acetal resin are added to the powder mixture and uniformly mixed to obtain a slurry. The components of the aforementioned dopant are listed in Table 1 below.

[0057] After granulating the slurry, it is pressed into a test sheet with a thickness of 200 μm using a tablet press. The test sheet is sintered at 1300 °C for 1 hour under 1% hydrogen (mixed in 99% nitrogen gas) to obtain a dielectric ceramic material. Then, copper end electrodes are added to the corresponding two sides of the dielectric ceramic material to conduct the evaluation tests described later, and the evaluation results are listed in Table 1 below.

[0058] Examples 2 to 25 and Comparative Examples 1 to 3

[0059] Examples 2 to 25 and Comparative Examples 1 to 3 are all manufactured in a method similar to that of Example 1. The difference is that Examples 2 to 25 and Comparative Examples 1 to 3 change the dosage of the dopant, and the specific conditions are shown in Table 1 below. Incidentally, the test sheet is used to evaluate the performance of the dielectric ceramic material, so the thickness of the test sheet is relatively thick to obtain more dielectric ceramic materials, and the dielectric ceramic materials with better performance are selected from these examples and comparative examples to manufacture the following multilayer ceramic capacitors. In the manufacture of the following multilayer ceramic capacitors, the thickness of the sheet is aimed at controlling the thickness of each dielectric ceramic layer in the multilayer ceramic capacitor to be 3.5 μm.

[0060] Manufacture of Multilayer Ceramic Capacitors

[0061] Application Example 1

[0062] The multilayer ceramic capacitor of Application Example 1 uses the composition formula of the dielectric ceramic material of Example 4, and 900 g of zirconia grinding balls (with a diameter of 2 mm) are used to grind at a grinding speed of 10 m / s for 8 times to obtain a slurry. The slurry undergoes processes of tape casting, printing, laminating, pressure equalization, cutting, debinding, sintering (sintered at 1300 °C for 1 hour under 3% hydrogen (mixed in 97% nitrogen gas)), and connecting copper end electrodes to manufacture a multilayer ceramic capacitor. The thickness of each dielectric ceramic layer in the multilayer ceramic capacitor is 3.5 μm, the number of layers is 10 layers, and the size of the multilayer ceramic capacitor is 3.0 mm × 1.5 mm × 1.0 mm (length × width × height), and the following evaluation tests are conducted on this capacitor, and the evaluation results are listed in Table 2 below.

[0063] Application Example 2 and Comparative Application Examples 1 to 6

[0064] Application Example 2 and Comparative Application Examples 1 to 6 were all manufactured in a method similar to that of Application Example 1. The difference is that in Application Example 2 and Comparative Application Examples 1 to 6, the average particle size of barium titanate in the dielectric ceramic material, the number of grinding times, and the sintering temperature were changed, and the specific conditions are shown in Table 2 below.

[0065] Evaluation Method

[0066] 1. Dielectric Constant (k-value, k - value) Test

[0067] For the dielectric constant test, the capacitance value was measured at 25°C, with a frequency of 1 kHz and an AC voltage of 1 V, and then converted to the dielectric constant of the dielectric ceramic material.

[0068] 2. Dissipation Factor (D f ) Test

[0069] For the dissipation factor test, the dissipation factors of the dielectric ceramic material and the multilayer ceramic capacitor were measured at 25°C, with a frequency of 1 kHz and an AC voltage of 1 V.

[0070] 3. Insulation Resistance (IR) Test

[0071] For the insulation resistance test, a DC voltage of 80 V was applied to the dielectric ceramic material and the multilayer ceramic capacitor at 25°C, and the resistance values of both were measured.

[0072] 4. Temperature Coefficient of Capacitance (TCC) Test

[0073] For the temperature coefficient of capacitance test, the capacitance values of the dielectric ceramic material (or multilayer ceramic capacitor) were measured at -55°C, 25°C, and 150°C. Based on the capacitance value measured at 25°C, the maximum change amounts (represented by ΔC -55 and ΔC 155 respectively) of the capacitance values measured at -55°C and 150°C relative to the capacitance value measured at 25°C were calculated for the dielectric ceramic material (or multilayer ceramic capacitor). This maximum change amount is the temperature coefficient of capacitance. When ΔC -55 and ΔC 155 ≤ 15%, the multilayer ceramic capacitor meets the X8R specification of the Electronic Industries Association.

[0074] 5. Capacitance (C) Test

[0075] The capacitance test applies an alternating current voltage of 1 V at a frequency of 1 kHz to the multilayer ceramic capacitor at 25°C, and measures its capacitance value.

[0076] 6. Breakdown voltage (BDV) test

[0077] The breakdown voltage test applies a voltage to the multilayer ceramic capacitor at a rate of 0.1 kV / s at 25°C to measure the voltage at breakdown, which is the breakdown voltage.

[0078] 7. Mean time to failure (MTTF) test

[0079] The mean time to failure test applies an electric field strength of 0.375 MV / cm to the multilayer ceramic capacitor at a temperature of 180°C to measure the time course change of its insulation resistance value. When the insulation resistance value reaches one-tenth of the initial measured value, record the time. This time is used as the insulation failure time of the multilayer ceramic capacitor, and 15 samples are statistically analyzed to obtain the time when 100% of the samples reach insulation failure as the mean time to failure. When the mean time to failure is greater than 10 hours, the multilayer ceramic capacitor has good life performance.

[0080] 8. Grain test

[0081] The grain test uses an electron microscope to observe the dielectric ceramic grains in the dielectric ceramic layer of the multilayer ceramic capacitor and measures their average particle size (D 50 ) and the volume fractions of the shell and core in the grains.

[0082] Table 1

[0083]

[0084] Table 1 (continued)

[0085]

[0086] Table 2

[0087]

[0088] Please refer to Table 1. Compared with Comparative Examples 1 to 3, the capacitance temperature coefficients of the dielectric ceramic materials of Examples 1 to 25 are not greater than 15% at -55°C and 150°C. It can be seen that a dopant containing a specific composition (containing manganese carbonate, barium carbonate, ytterbium oxide, vanadium pentoxide, and silicon dioxide) can reduce the capacitance temperature coefficient of the prepared dielectric ceramic material.

[0089] Please refer to Table 2. Compared with Comparative Application Examples 1 to 6, the capacitance temperature coefficient of the multilayer ceramic capacitors of Application Examples 1 to 2 is smaller and the mean time to failure is longer. Therefore, barium titanate particles with an average particle size of 0.20 μm to 0.40 μm and the dopant of Example 4 combined with 8 times of grinding treatment can produce grains including a core and a shell, and the volume of the shell is 25 volume fractions to 60 volume fractions, thereby reducing the capacitance temperature coefficient of the produced multilayer ceramic capacitors and prolonging their mean time to failure.

[0090] In summary, the manufacturing method of the dielectric ceramic material of the present invention uses barium titanate particles with a specific average particle size, a grinding treatment with a specific number of grinding times, and a dopant with a specific composition to manufacture a dielectric ceramic material including grains with a core-shell structure, and these grains have a shell with a specific volume fraction, so as to improve the capacitance temperature coefficient of the dielectric ceramic material between -55 °C and 150 °C, thereby enhancing the high-temperature thermal stability of the produced multilayer ceramic capacitors and improving their life performance.

[0091] Although the present invention has been disclosed as above in embodiments, it is not intended to limit the present invention. Those skilled in the art in the technical field to which the present invention pertains can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to that defined by the claims.

[0092]

Symbol Explanation

[0093] 100: Method

[0094] 110, 120, 130, 140: Operations

[0095] 200: Dielectric ceramic material

[0096] 210: Grains

[0097] 211: Core

[0098] 212: Shell

[0099] 220: Region

[0100] 300: Multilayer ceramic capacitor

[0101] 310: Stacked structure

[0102] 310A, 310B: End faces

[0103] 311: Dielectric ceramic layer

[0104] 312: Internal electrode

[0105] 320: External electrode.

Claims

1. A manufacturing method of a dielectric ceramic material, characterized in that, comprising: Provided are barium titanate (BaTiO 3 ) particles and a dopant, wherein the dopant comprises: Ytterbium oxide (Yb 2 O 3 ); Silicon dioxide (SiO 2 ); Manganese carbonate (MnCO 3 ) Barium carbonate (BaCO 3 ); and Vanadium pentoxide (V 2 O 5 ); wherein the average particle size of the barium titanate particles is greater than 0.15 μm and not greater than 0.45 μm, and based on the amount of the barium titanate particles being 100 mole percentages, the amount of ytterbium oxide is greater than 0 mole percentages and not greater than 3.2 mole percentages; mixing the barium titanate particles, the dopant and the dispersant, and performing a grinding process to obtain a powder mixture, wherein the number of grinding times of the grinding process is 5 to 9 times; adding a binder to the powder mixture, and performing a molding process to obtain a sheet; and performing a sintering process on the sheet to obtain the dielectric ceramic material, wherein the sintering temperature of the sintering process is 1200 °C to 1420 °C, and the sintering time of the sintering process is 0.5 hour to 4.5 hours.

2. The manufacturing method of the dielectric ceramic material according to claim 1, characterized in that, based on the amount of the barium titanate particles being 100 mole percentages, the amount of silicon dioxide is greater than 0.9 mole percentages and not greater than 3.8 mole percentages, the amount of vanadium pentoxide is 0.05 mole percentages to 1.0 mole percentages, the amount of manganese carbonate is 0.10 mole percentages to 0.35 mole percentages, and the amount of barium carbonate is 1.0 mole percentages to 4.0 mole percentages.

3. The manufacturing method of the dielectric ceramic material according to claim 1, characterized in that, The dopant further comprises dysprosium oxide (Dy 2 O 3 ), and based on the amount of the barium titanate particles, the amount is 100 mole percent, and the amount of the dysprosium oxide is less than 1.86 mole percent.

4. The manufacturing method of the dielectric ceramic material according to claim 1, characterized in that, The dopant also contains at least one member of the group consisting of magnesium carbonate (MgCO 3 ), yttrium oxide (Y 2 O 3 ), calcium zirconium trioxide (CaZrO 3 ), and calcium carbonate (CaCO 3 ).

5. The manufacturing method of the dielectric ceramic material according to claim 1, characterized in that, based on the amount of the barium titanate particles being 100 mole percentages, the amount of the dopant is 5 mole percentages to 20 mole percentages.

6. The manufacturing method of the dielectric ceramic material according to claim 1, characterized in that, the grinding speed of the grinding process is 5 m / s to 15 m / s.

7. The manufacturing method of the dielectric ceramic material according to claim 1, characterized in that, the atmosphere of the sintering process contains 0.5% to 3.5% of hydrogen.

8. A dielectric ceramic material, characterized in that, is prepared by using the manufacturing method of the dielectric ceramic material according to any one of claims 1 to 7, wherein the dielectric ceramic material comprises: a plurality of grains, wherein each of these grains comprises a core and a shell; wherein the average particle size of each of these grains is 0.15 μm to 0.25 μm, and based on the volume of each of these grains being 100 volume fractions, the volume of the core is 40 volume fractions to 75 volume fractions, and the volume of the shell is 25 volume fractions to 60 volume fractions.

9. The dielectric ceramic material according to claim 8, characterized in that, the capacitance temperature coefficients of the dielectric ceramic material at -55 °C and 150 °C are both not greater than 15%.

10. A multilayer ceramic capacitor, characterized in that, comprising: a stacked structure, the stacked structure comprising: a plurality of dielectric ceramic layers, formed by the dielectric ceramic material according to claim 8 or 9, wherein these dielectric ceramic layers are stacked in sequence; and A plurality of internal electrode layers are respectively disposed between every two adjacent ones of these dielectric ceramic layers and alternately protrude from opposite first and second end faces of the stacked structure in sequence; and Two external electrodes are respectively disposed on the first end face and the second end face and are respectively electrically connected to the internal electrode layers protruding from the first end face or the second end face.

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