Laminated ceramic capacitor

Abstract

Provided is a laminated ceramic capacitor, comprising a plurality of segregated particles with a size of 10 microns or less in an effective capacitance part; wherein the segregated particles are most in direct contact with the internal electrode layers, and the segregated particles have ingredients comprising Si, an alkaline earth metal, a rare earth element or a combination thereof. The segregated particles comprising Si are in a higher concentration than that of the segregated particles comprising the alkaline earth metal, and the segregated particles comprising the alkaline earth metal are in a higher concentration than that of the segregated particles comprising the rare earth element. The laminated ceramic capacitor of the present invention can maintain a high capacitance and avoid insulation resistance degradation resulting from a high temperature or a high voltage, thereby demonstrating a good high-temperature operating life and good reliability.

Description

[Technical Field]

[0001] This invention relates to a multilayer ceramic capacitor. [Previous Technology]

[0002] With the advancement of electronic devices, multilayer ceramic capacitors are required to have higher reliability.

[0003] Generally speaking, the degradation of the high-temperature load life of multilayer ceramic capacitors with barium titanate (BaTiO3) as the main component is considered to be due to the accumulation of oxygen defects generated during the sintering process near the internal electrode layer during high-temperature load testing. When the oxygen defect concentration exceeds the critical concentration, a short circuit occurs, leading to insulation degradation. On the other hand, segregated phases are generated in the form of paraelectric particles, so they not only do not have oxygen defects, but also have a low dielectric constant, and still have high insulation resistance even under high-temperature load testing conditions.

[0004] For example, Patent Document 1 describes that in order to solve the problem of electric field inhomogeneity caused by segregated phase, segregated phase containing rare earth elements is segregated in a manner that contacts the internal electrode layer, thereby further improving the high temperature load life and relative permittivity.

[0005] However, in the multilayer ceramic capacitor shown in Patent Document 1, if the content of rare earth oxides is too low, it becomes difficult to generate segregated phases, and the non-uniformity of the electric field caused by the segregated phases cannot be eliminated. Furthermore, if the content of rare earth oxides is too high, there will be a problem that the high-temperature load life cannot be improved. Therefore, although a certain effect can be seen in Patent Document 1, there is still room for improvement.

[0006] [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Patent Application Publication No. 2020-021819 [Summary of the Invention]

[0007] [The problem the invention aims to solve]

[0008] In view of this, the present invention aims to provide "a multilayer ceramic capacitor that maintains high capacitance while avoiding insulation resistance degradation under high temperature and high voltage, thereby further improving high temperature load life and having excellent reliability".

[0009] [Technical means to solve the problem]

[0010] This invention provides a multilayer ceramic capacitor, comprising: a capacitor body comprising: a plurality of dielectric layers and a plurality of internal electrode layers stacked alternately; wherein the region where the dielectric layers and the internal electrode layers are stacked alternately is defined as an effective capacitance portion; a plurality of segregated particles having a size of less than 10 micrometers and present in the effective capacitance portion; wherein most of the plurality of segregated particles are in direct contact with the internal electrode layers, the composition of the plurality of segregated particles includes any or a combination of silicon, alkaline earth metals and rare earth elements, and the concentration of the plurality of segregated particles containing silicon is greater than the concentration of the plurality of segregated particles containing alkaline earth metals, and the concentration of the plurality of segregated particles containing alkaline earth metals is greater than the concentration of the plurality of segregated particles containing rare earth elements; and two external electrodes respectively disposed at both ends of the capacitor body and each electrically connected to the internal electrode layers.

[0011] The multilayer ceramic capacitor of the present invention has the composition (especially silicon element), size and distribution characteristics of the segregated particles, so it can maintain high capacitance and avoid insulation resistance degradation caused by high temperature and high voltage, thereby improving the high temperature load life of the multilayer ceramic capacitor and achieving excellent reliability.

[0012] In one embodiment, the alkaline earth metal comprises either or a combination of magnesium and calcium.

[0013] Preferably, the alkaline earth metal comprises magnesium and calcium, and the concentration of the complex segregated particles comprising magnesium is greater than the concentration of the complex segregated particles comprising calcium.

[0014] In one embodiment, the rare earth element includes dysprosium.

[0015] In one embodiment, the size of the complex segregated particles is from 0.1 micrometers to 10 micrometers.

[0016] According to the present invention, the upper limit and lower limit of the size of the complex segregated particles are respectively the longest length of the largest segregated particle and the longest length of the smallest segregated particle, and do not refer to the average length.

[0017] In one embodiment, the shape of the complex segregated particles includes any or a combination of flat, amorphous and spherical shapes.

[0018] In one embodiment, the segregated particles comprise a composite oxide and a single oxide; wherein the composite oxide comprises at least two elements selected from silicon, magnesium, calcium and dysprosium, and the single oxide comprises silicon, magnesium, calcium, dysprosium or manganese.

[0019] Preferably, the single oxide comprises either silicon dioxide (SiO2) or magnesium oxide (MgO) or a combination thereof.

[0020] In one embodiment, the multilayer ceramic capacitor has a multilayer direction, a length direction and a width direction that are perpendicular to each other, and the total length of the segregated particles along the length direction is more than 90% based on the sum of the lengths of all the segregated particles.

[0021] According to the present invention, the length of the segregated particles along the length direction refers to the length parallel to the inner electrode layer. Preferably, the length of the segregated particles along the length direction refers to the length parallel to the extension direction of the inner electrode layer. More preferably, the length refers to the longest horizontal length.

[0022] As can be seen from the embodiments of this case, most segregated particles extend along the internal electrode layer and are flat, while others are irregular or spherical. No particles have been observed extending in the stacking direction while breaking through several internal electrode layers. Therefore, the segregated particles of this invention measure the maximum length along the length direction of the stacked ceramic capacitor, rather than its area, diameter, or diagonal, and thus possess discriminatory power and rationality. In other words, even if the shape of the plurality of segregated particles is irregular, the length of the plurality of segregated particles is still measured along its longest horizontal length parallel to the internal electrode layer.

[0023] In one embodiment, the internal electrode layer includes a plurality of effective electrode portions and a plurality of discontinuous portions; wherein each of the plurality of effective electrode portions is electrically connected to the external electrode, and the plurality of discontinuous portions includes a plurality of holes and a plurality of filling portions, and each of the plurality of holes and the plurality of filling portions is surrounded by the dielectric layer and the effective electrode portions.

[0024] According to the present invention, since the plurality of holes and the plurality of filling portions are located in the inner electrode layer, the "total length of the segregated particles in direct contact with the inner electrode layer" includes the total length of the segregated particles that are in direct contact with both the plurality of effective electrode portions and any one of the plurality of holes and the plurality of filling portions. Furthermore, the segregated particles that are in direct contact with the plurality of holes refer to those whose outer contours partially overlap with the outer contours of the holes. Finally, if the plurality of filling portions are segregated particles, their longest horizontal length is also included in the "total length of the segregated particles in direct contact with the inner electrode layer".

[0025] In one embodiment, the dielectric layer has principal component particles, the principal component particles comprising any or a combination of magnesium (Mg) oxide, calcium (Ca) oxide, dysprosium (Dy) oxide, manganese (Mn) oxide and zirconium (Zr) oxide dissolved in barium titanate having a perovskite structure.

[0026] [Effects of the Invention]

[0027] The present invention can provide a multilayer ceramic capacitor that can maintain high capacitance while avoiding insulation degradation under high temperature and high voltage.

Implementation Method

[0029] Figure 1 is a cross-sectional view of the multilayer ceramic capacitor of the present invention along the stacking direction, and is for illustrative purposes only and not a scale representation. The multilayer ceramic capacitor 1 includes a capacitor body 4, which includes: a plurality of dielectric layers 2 and a plurality of internal electrode layers 3 stacked alternately; wherein the area where the dielectric layers 2 and the internal electrode layers 3 are stacked alternately is defined as an effective capacitance portion 40; and two external electrodes 5, which are respectively disposed at both ends of the capacitor body 4 and are electrically connected to the internal electrode layers 3. In other words, as shown in Figure 1, the effective capacitance portion 40 is defined as the area within the dashed box, and when viewed from the stacking direction, the effective capacitance portion 40 is the area where the dielectric layers 2 and the internal electrode layers 3 overlap one-to-one.

[0030] Figure 2 is an enlarged view of observation area A in the effective capacity portion 40 of Figure 1, to clearly illustrate the types and distribution of the multiple segregated particles 7 present in the effective capacity portion 40 of the present invention. The internal electrode layer 3, dielectric layer 2 and segregated particles 7 shown in Figure 2 are not actual size proportions. The internal electrode layer 3 has an effective electrode portion 3a electrically connected to an external electrode (not shown) and multiple discontinuous portions 3b. The discontinuous portions 3b are surrounded by the dielectric layer 2 and the effective electrode portion 3a. The size of the segregated particles 7 is less than 10 micrometers, mainly including composite oxides 7a, which have flat, amorphous and spherical shapes, mostly flat, and the composite oxides 7a are not limited to crystalline phases. The discontinuous portions 3b include those completely occupied by the composite oxides 7a (only 7a is indicated, 3b is not indicated separately), those partially occupied by the composite oxides 7a, and those not occupied by the segregated particles 7, and are pores.

[0031] The segregated particles 7 may also contain a single oxide 7b, which may be flat, amorphous, or slightly spherical, and the single oxide 7b is not limited to a crystalline phase. The composite oxide 7a and the single oxide 7b are present at the interface between the discontinuity portion 3b or the effective electrode portion 3a and the dielectric layer 2. The discontinuity portion 3b may also include portions wholly or partially occupied by the single oxide 7b.

[0032] Regarding the composite oxide 7a, it comprises a composite oxide with Si and Mg as the main components. Preferably, the composite oxide 7a comprises a composite oxide containing Si, Mg, Ca and Dy.

[0033] Regarding the single oxide 7b, for example, it may include single oxides such as SiO2, MgO, CaO, Dy2O3, and MnO. Preferably, the single oxide 7b is SiO2 or MgO.

[0034] It should be noted that, based on the distribution of segregated particles, the present invention can be divided into segregated particles that are in direct contact with the effective electrode portion and segregated particles that are not in direct contact with the internal electrode layer, that is, segregated particles that are spaced apart from the internal electrode layer. The present invention uses a scanning electron microscope (SEM) and an energy-dispersive X-ray spectroscopy (EDS) at 3000x magnification to measure 20 arbitrary points in any cross-section of the effective capacitance portion in the stacking direction of the multilayer ceramic capacitor, and obtains SEM and EDS sample images.

[0035] As shown in Figure 3, the effective electrode portion 3a and the discontinuous portion 3b, especially the holes (dark gray or black blocks), can be clearly seen in the SEM sampling image at 3000x magnification.

[0036] As shown in Figure 4, it is an EDS sampling photograph at 3000x magnification, showing the elemental concentration distribution of Si, Mg, Ca, and Dy. The following points are noted: First, most of the segregated particles are in direct contact with the internal electrode layer (including the effective electrode portion 3a and the discontinuous portion 3b). Second, the longest horizontal length of each segregated particle can be measured based on the distribution position of the segregated particles containing Si, Mg, Ca, and Dy, and the longest horizontal length of each segregated particle is less than 10 micrometers. Third, the concentration of segregated particles containing Si is significantly higher than that containing Mg, Ca, and Dy, while the concentration of segregated particles containing Mg is the second highest. Fourth, after comparing the positions, it can be further distinguished that the segregated particles are either composite oxide 7a or single oxide 7b.

[0037] As shown in Figure 5, in the schematic diagram of the EDS sampling photograph, after visually classifying the segregated particles that are "in direct contact with the internal electrode layer (including the effective electrode portion 3a and the discontinuous portion 3b)" and "not in direct contact with the internal electrode layer", the maximum length L of each segregated particle in the length direction of the multilayer ceramic capacitor is measured to obtain the sum of the sizes of the segregated particles that are "in direct contact with the internal electrode layer" and "not in direct contact with the internal electrode layer" (i.e. the sum of the maximum length L in the length direction of the multilayer ceramic capacitor), and the respective proportions are calculated based on the sum of the two as the denominator.

[0038] Figure 6 is an enlarged view of the observation area B in Figure 2. The dielectric layer 2 is a ceramic sintered body containing principal component particles 6. The principal component particles 6 are polycrystalline and contain barium titanate (BaTiO3) with a perovskite structure, and a plurality of oxides dissolved in BaTiO3, thereby adjusting the dielectric constant of BaTiO3 to ensure capacitive characteristics. Preferably, the oxides contain oxides of Mg, Ca, Dy, and Mn. Furthermore, the maximum particle size of the principal component particles 6 does not exceed the thickness of the dielectric layer 2.

[0039] It should be noted that even if the main component particles 6 contain multiple types of oxides, they still maintain the perovskite structure of BaTiO3, and the content of oxides is not fixed. Furthermore, the oxides dissolved in BaTiO3 include, for example: MgO, CaO, Dy2O3, MnO, ZrO2, etc.

[0040] In summary, the multilayer ceramic capacitor of the present invention can maintain high capacitance while avoiding the degradation of insulation resistance caused by high temperature and high voltage, so as to achieve excellent reliability.

[0041] During the sintering process, the internal electrode layer is formed into a plate shape by passing through the sintered metal powder. The metal powder used as the internal electrode layer is preferably Ni powder or an alloy powder with Ni as the main component.

[0042] It should be noted that, in one cross-section of the stacking direction of the multilayer ceramic capacitor, although the internal electrode layer appears discontinuous, other cross-sections of the stacking direction of the multilayer ceramic capacitor show that the effective electrode portion can ensure the electrical connection between the internal electrode layer and the external electrode.

[0043] The external electrode achieves electrical connection with the internal electrode layer through sintering metal powder and is bonded to the capacitor body by softening the glass composition. Preferably, the metal powder used as the external electrode is Cu or an alloy powder with Cu as the main component. Furthermore, the glass composition of the external electrode does not excessively diffuse into the capacitor body 4. Also, although not shown, after forming the external electrode, a Ni plating layer and / or a Sn plating layer may be formed to improve mounting performance, thereby forming a multilayer ceramic capacitor.

[0044] The following example illustrates a method for manufacturing a multilayer ceramic capacitor, but the present invention is not limited to this manufacturing method.

[0045] First, after weighing the required amount of barium titanate powder and additive powder, the powders are mixed evenly in water using a ball mill and then dried to obtain dielectric powder. The barium titanate powder can be prepared by solid-state method, hydrothermal synthesis method, oxalate method, etc.; the additive powder contains compound powders that will form oxides of Mg, Ca, Si, Dy and Mn after sintering; wherein, the specific surface area of ​​the additive powder is larger than that of the barium titanate powder, so as to facilitate the formation of main component particles and segregated particles after sintering.

[0046] Furthermore, the additive powder may contain ZrO2. This can promote the growth of the main component particles, promote the formation of segregated particles, and reduce the sintering temperature during sintering.

[0047] Subsequently, the obtained dielectric powder is mixed with solvents such as ethanol or toluene, binders such as polyvinyl butyral resin (PVB Resin), and plasticizers such as phthalate ester using a ball mill to obtain a dielectric slurry. The mixing time can be determined based on the specific surface area of ​​the dielectric powder in the dielectric slurry. Afterward, the obtained dielectric slurry sheet is formed onto a polyethylene terephthalate (PET) film using forming equipment such as a coating machine. The thickness of the sheet can be designed according to the capacitance of the multilayer ceramic capacitor.

[0048] A conductive paste serving as the internal electrode layer is printed onto the sheet, and a green body is obtained after lamination and cutting processes. Regarding the conductive paste, a conductive paste can be used, for example, a mixture of Ni powder with a solvent such as terpineol and a binder such as ethyl cellulose or PVB resin. Regarding the printing method, screen printing or gravure printing can be used. The average particle size of the Ni powder is preferably 0.2 to 0.4 micrometers to maintain the effective area of ​​the capacitor and increase discontinuities, thereby promoting the formation of segregated particles.

[0049] Subsequently, the degreasing temperature of the embryo body is preferably 350°C to 500°C, and it is carried out in an atmosphere of inactive gas to avoid excessive oxidation of the internal electrode layer and to control the residual carbon content to less than 4% of the weight of the degreased embryo body, thereby avoiding the influence of the formation of main component particles and segregated particles.

[0050] Subsequently, the degreased green body is sintered to obtain a sintered body. The maximum sintering temperature and holding time can be determined based on the composition and specific surface area of ​​the dielectric powder. Sintering is carried out in an atmosphere of inert gas, preferably in an atmosphere where the oxygen partial pressure is controlled one order lower than the equilibrium oxygen partial pressure of Ni. For example, when the maximum sintering temperature is 1000℃, it is controlled at 10-11.4 atm to avoid excessive oxidation of the internal electrode layer.

[0051] During the sintering process, the temperature at which Ni powder forms a plate is approximately 1000°C to 1100°C. Because the temperature at which the main component particles begin to sinter is higher than the temperature at which Ni powder forms a plate, the Ni in the internal electrode layer becomes over-sintered during the densification process of the main component particles. Therefore, the internal electrode layer will form effective electrode portions and multiple discontinuous portions. On the other hand, during the growth and densification of the main component particles, the oxides of Mg, Ca, Si, and Dy, which are added as additives, are forced to be pushed from the dielectric layer to the interface between the internal electrode layer and the dielectric layer, resulting in segregation and forming segregated particles that are either composite oxides or single oxides.

[0052] Thus, the segregated particles become directly in contact with the internal electrode layer and exist at the interface between the discontinuity or the effective electrode portion and the dielectric layer. Furthermore, the discontinuity becomes partially or completely occupied by the segregated particles.

[0053] However, if excessive segregated particles are generated, the segregated particles will become abnormal particles, which may cause cracks in the sintered capacitor body. Therefore, appropriate adjustments can be made according to the specific surface area of ​​the dielectric powder in the dielectric paste or the sintering temperature.

[0054] The sintered body is subjected to a re-oxidation treatment, and the internal electrodes at both ends of the sintered body are exposed by tumbling to obtain the capacitor body. The re-oxidation treatment is carried out at 900°C to 1050°C in humidified N2. Subsequently, Cu paste is coated onto the capacitor body, and sintering is performed to form external electrodes. Then, Ni plating and Sn plating are formed sequentially to obtain a multilayer ceramic capacitor.

[0055] The present invention will be described in further detail below, but the present invention is not limited to these embodiments.

[0056] <Preparation Example 1>

[0057] (1) Fabrication of multilayer ceramic capacitors

[0058] First, in order to form oxides of Mg, Ca, Dy, and Mn dissolved in BaTiO3 having a perovskite structure, BaTiO3 powder with a specific surface area of ​​3 m² / g and an average particle size of 0.2 to 0.3 μm as determined by SEM was prepared as the main component. MgO powder with a specific surface area of ​​5 m² / g, CaCO3 powder with a specific surface area of ​​10 m² / g, SiO2 powder with a specific surface area of ​​10 m² / g, Dy2O3 powder with a specific surface area of ​​10 m² / g, and MnO powder with a specific surface area of ​​6 m² / g were prepared as additives. The raw material powders were prepared in the following proportions: 100 mol BaTiO3 powder, 1 mol MgO powder, 1 mol CaCO3 powder, 1 mol SiO2 powder, 0.8 mol Dy2O3 powder, and 0.2 mol MnO powder. The raw material powder was mixed evenly with pure water and ZrO2 balls using a ball mill and then dried to obtain dielectric powder.

[0059] Dielectric powder is mixed with PVB resin (as a binder), phthalate (as a plasticizer), and dispersant in a ball mill in a solvent of ethanol and toluene to obtain a dielectric slurry. During the mixing process, the dielectric powder is also pulverized due to the use of ZrO2 balls in the ball mill. If the mixing time is increased, the specific surface area of ​​the dielectric powder in the dielectric slurry will increase.

[0060] In this embodiment, seven types of dielectric slurries with specific surface areas ranging from 3.5 m² / g to 8.5 m² / g were prepared by varying the mixing time. The specific surface area was determined by taking a small amount of each dielectric slurry, drying it at 150°C, and then degreasing it in the atmosphere at 350°C to obtain dielectric powder. The obtained dielectric powder was then measured using a specific surface area measuring device. It should be noted that this embodiment uses fresh ZrO₂ spheres; therefore, when mixing with ZrO₂ spheres, no Zr component is introduced due to the ZrO₂ spheres.

[0061] Subsequently, the seven types of dielectric pastes were formed into sheets with a thickness of 4 micrometers.

[0062] Next, a Ni paste composed of Ni powder with an average particle size of 0.3 micrometers, ethyl cellulose, terpineol, and a dispersant is prepared. Using a screen printing machine, a plurality of internal electrodes in the shape of 32 mm × 16 mm are printed on a sheet using this paste. The thickness of the internal electrode print is 1 to 2 micrometers. 350 ceramic sheets with the internal electrode print are stacked and hot-pressed together using hot isostatic pressing. The sheets are then cut into 32 mm × 16 mm shapes to obtain a green body. The green body is thoroughly degreased in an atmosphere of N2 at a maximum temperature of 400°C.

[0063] Subsequently, the fully degreased green body is sintered. To prevent Ni from being oxidized, a humidified N2 and H2 mixture gas is used and controlled at an oxygen partial pressure lower than the equilibrium oxygen partial pressure of Ni.

[0064] In this embodiment, the seven types of green bodies were subjected to sintering temperatures of 1220°C, 1250°C and 1280°C respectively.

[0065] The sintered body obtained after sintering the green body is re-oxidized at 900°C in N2. Then, the end faces of the sintered body are tumble-ground in water until the internal electrode layer is exposed. After drying, Cu paste is applied and sintered in N2 at a maximum temperature of 800°C to form the external electrode. Subsequently, a Ni plating layer and a Sn plating layer are formed sequentially to obtain a multilayer ceramic capacitor.

[0066] (2) Evaluation

[0067] Multilayer ceramic capacitors made using the above seven types of dielectric pastes were designated as samples 1 to 21, and the following data were obtained: whether there were segregated particles, the upper and lower limits of segregated particles (i.e., the maximum horizontal length of the largest segregated particle and the maximum horizontal length of the smallest segregated particle), the top two components of the complex segregated particles, the percentage of the total length of the segregated particles in direct contact with the internal electrode layer (i.e., the percentage of the total length of the segregated particles in direct contact with the internal electrode layer to the total length of all segregated particles), and capacitance and high-temperature load tests were performed.

[0068] <Segregated Particles>

[0069] Samples 1 to 21 were ground until their internal cross-sections in the stacking direction were exposed. The sampling range was observed using SEM at 3000x magnification, and elemental analysis of the same range was performed using EDS. The sampling range consisted of 20 arbitrary locations within the effective capacity area, and the same observation was performed on these 20 locations. The lengths of segregated particles in these 20 sampling ranges were measured visually using SEM and EDS images. The results of the lengths of the minimum and maximum segregated particles for each sample are shown in Tables 1 to 3. In addition, the lengths of all segregated particles in these 20 sampling ranges were measured visually using SEM and EDS images. Based on the distribution of the segregated particles, they were divided into segregated particles that were in direct contact with the internal electrode layer and segregated particles that were not in direct contact with the internal electrode layer. The principal components (i.e., the two elements with the highest concentrations) of the multiple segregated particles were recorded, and the results are shown in Tables 1 to 3. The SEM images and EDS analysis diagrams of the representative segregated particles in this preparation example are shown in Figures 3 and 4.

[0070] <Capacitor>

[0071] The capacitance of samples 1 to 21 was measured using a digital LCR meter (purchased from Agilent Technologies, model: 4294A). Ten samples were measured at 25°C, 1 kHz frequency, and 1.0 Vrms measurement voltage. The average values ​​are recorded in Tables 1 to 3.

[0072] <High Temperature Load Test>

[0073] The insulation resistance of test samples 1 to 21 was measured, and the insulation resistance was measured simultaneously with a load voltage of 150V for 1000 hours in a constant temperature bath at 125°C in the atmosphere. 40 samples were measured for each test. Insulation resistance below 1×10 6Ω was judged as deterioration, and the number of deteriorated samples was recorded in Tables 1 to 3.

[0074] (3) Evaluation Results

[0075] Tables 1 to 3 record the sintering results of samples 1 to 21 under three conditions: sintering temperature of 1220℃, 1250℃, and 1280℃.

[0076] Table 1: Sintering temperature, specific surface area of ​​dielectric powder, length of segregated particles (i.e., upper and lower limits), highest concentration of segregated particles, second highest concentration of segregated particles, percentage of total length of segregated particles in direct contact with the internal electrode layer, capacitance, and number of deteriorations for samples 1 to 7 (i.e., Comparative Examples 1 and 2, and Examples 3 to 7). Sample number Dielectric powder Sintering temperature: 1220℃ Comparison Table area (m 2 / g) Segregated particles capacitance (μF) Deterioration quantity length (μm) Highest concentration of ingredients Second highest concentration of components The percentage of the total length in direct contact with the internal electrode layer (%) 1 Comparative Example 1 3.5 Unbiased particles Si Mg N / A 9.5 3 / 40 2 Comparative Example 2 4.0 Unbiased particles Si Mg N / A 10.0 1 / 40 3 Example 1 4.7 0.1~2.2 Si Mg 92 10.2 0 / 40 4 Example 2 6.0 1.8~3.5 Si Mg 94 10.3 0 / 40 5 Example 3 7.3 3.8~4.2 Si Mg 94 10.4 0 / 40 6 Example 4 8.0 3.9~5.7 Si Mg 97 10.6 0 / 40 7 Example 5 8.5 4.2~5.9 Si Mg 97 10.9 0 / 40

[0077] Table 2: Sintering temperature, specific surface area of ​​dielectric powder, length of segregated particles (i.e., upper and lower limits), highest concentration of segregated particles, second highest concentration of segregated particles, percentage of total length of segregated particles in direct contact with the internal electrode layer, capacitance, and number of deteriorations for samples 8 to 14 (i.e., Comparative Example 3 and Examples 6 to 11). Sample number Dielectric powder Sintering temperature: 1250℃ Comparison Table area (m 2 / g) Segregated particles capacitance (μF) Deterioration quantity length (μm) Highest concentration of ingredients Second highest concentration of components The percentage of the total length in direct contact with the internal electrode layer (%) 8 Comparative Example 3 3.5 Unbiased particles Si Mg N / A 10.0 3 / 40 9 Example 6 4.0 0.6~1.1 Si Mg 93 10.4 0 / 40 10 Example 7 4.7 0.9~2.5 Si Mg 93 10.4 0 / 40 11 Example 8 6.0 1.8~3.8 Si Mg 95 10.7 0 / 40 12 Example 9 7.3 4.0~5.5 Si Mg 96 10.6 0 / 40 13 Example 10 8.0 5.1~6.0 Si Mg 97 10.8 0 / 40 14 Example 11 8.5 5.9~8.8 Si Mg 98 11.1 0 / 40

[0078] Table 3: Sintering temperature, specific surface area of ​​dielectric powder, length of segregated particles (i.e., upper and lower limits), highest concentration of segregated particles, second highest concentration of segregated particles, percentage of total length of segregated particles in direct contact with the internal electrode layer, capacitance, and number of deteriorations for samples 15 to 21 (i.e., Examples 12 to 17 and Comparative Example 4). Sample number Dielectric powder Sintering temperature: 1280℃ Comparison Table area (m 2 / g) Segregated particles capacitance (μF) Deterioration quantity length (μm) Highest concentration of ingredients Second highest concentration of components The percentage of the total length in direct contact with the internal electrode layer (%) 15 Example 12 3.5 0.5~1.0 Si Mg 92 10.3 0 / 40 16 Example 13 4.0 0.8~1.7 Si Mg 93 10.6 0 / 40 17 Example 14 4.7 1.2~2.5 Si Mg 93 10.7 0 / 40 18 Example 15 6.0 2.0~4.0 Si Mg 96 10.8 0 / 40 19 Example 16 7.3 4.7~6.2 Si Mg 96 10.9 0 / 40 20 Example 17 8.0 7.0~9.2 Si Mg 97 10.9 0 / 40 twenty one Comparative Example 4 8.5 7.1~11.5 Si Mg 97 11.6 4 / 40

[0079] As shown in Table 1, firstly, samples 1, 2, and 8 did not form segregated particles and showed insulation resistance degradation, thus they are Comparative Examples 1 to 3. Meanwhile, the length of the segregated particles in sample 21 (i.e., the maximum length in the longitudinal direction of the multilayer ceramic capacitor) exceeded 10 micrometers, and insulation resistance degradation occurred. Furthermore, microcracks were observed near the segregated particles. It was determined that the size of the segregated particles exceeding 10 micrometers easily leads to the formation of microcracks and causes insulation resistance degradation, thus this is Comparative Example 4. It can be seen that segregated particles smaller than 10 micrometers can effectively prevent insulation resistance degradation.

[0080] Second, as can be seen from samples 1 to 7, increasing the specific surface area of ​​the dielectric powder in the dielectric slurry can promote the formation of segregated particles and increase the size of the segregated particles. As can be seen from samples 2, 9, and 16 in Tables 1 to 3, increasing the sintering temperature can also promote the formation of segregated particles and increase the size of the segregated particles. As can be seen from samples 1 to 7 in Table 1, the formation of segregated particles and the increase in the size of the segregated particles can increase the capacitance value and reduce the amount of degradation.

[0081] Therefore, in order to maintain high capacitance and at the same time avoid degradation of insulation resistance, the size of the segregated particles must be controlled to be below 10 micrometers. In this preparation example, the size of the segregated particles is preferably between 0.1 micrometers and 10 micrometers. This can be appropriately adjusted according to the specific surface area of ​​the dielectric powder in the dielectric slurry or the sintering temperature. For example, for a specific surface area of ​​8.5 m² / g of dielectric powder in the dielectric slurry, the sintering temperature can be set to 1220℃~1250℃. For a sintering temperature of 1280℃, the specific surface area of ​​the dielectric powder in the dielectric slurry can be set to 3.5 m² / g~8.0 m² / g.

[0082] Furthermore, it is known that when the specific surface area of ​​the dielectric powder in the dielectric slurry is reduced, if the sintering temperature is too low, the main component particles will not be sintered sufficiently, making it more difficult to form segregated particles and more likely to cause insulation degradation.

[0083] Furthermore, as shown in Tables 1 to 3, the total length of the segregated particles in direct contact with the internal electrode layer accounts for more than 90%. As shown in Figure 4, the segregated particles in contact with the effective electrode portion exist in the discontinuous portion or at the interface between the effective electrode portion and the dielectric layer. Furthermore, the segregated particles can be flat, amorphous, or spherical.

[0084] Furthermore, as shown in Figure 4, among the complex segregated particles, there exist segregated particles in which different elements are detected within the same segregated particle, and these segregated particles are composite oxides. This confirms the existence of composite oxides, and that the complex discontinuity includes a discontinuity completely occupied by segregated particles.

[0085] Furthermore, as shown in Figure 4, the concentrations of Si and Mg in the complex segregated particles are higher than those of Ca and Dy, confirming the presence of a composite oxide containing Si and Mg as the main components. In addition, relatively low concentrations of Ca and Dy were also detected in the same segregated particle, indicating the presence of a composite oxide containing Si, Mg, Ca, and Dy.

[0086] Thus, the present invention controls the size of the segregated particles to be less than 10 micrometers. The segregated particles contain a composite oxide with Si and Mg as the main components. The discontinuous part includes the part completely occupied by the segregated particles. The total length of the segregated particles in direct contact with the internal electrode layer accounts for more than 90% (that is, the total length of the segregated particles separated from the internal electrode layer accounts for less than 10%). The segregated particles exist at the interface between the discontinuous part or the effective electrode part and the dielectric layer. Therefore, the multilayer ceramic capacitor of the present invention has the effect of maintaining high capacitance and improving high temperature load life at the same time.

[0087] Furthermore, in addition to the composite oxide, the segregated particles also contain small amounts of single oxides such as SiO2, MgO, CaO, and Dy2O3. Additionally, in this embodiment, because the proportion of added MnO is small, MnO was not detected in the segregated particles.

[0088] <Preparation Example 2>

[0089] (1) Fabrication of multilayer ceramic capacitors

[0090] In the same proportion of raw material powder as in Example 1, ZrO2 powder with a specific surface area of ​​10 m² / g was added. The addition ratio (i.e., molar ratio) of ZrO2 compared to 100 mol of BaTiO3 was 0.01 mol, 0.05 mol, 0.10 mol, 0.30 mol, and 0.50 mol, respectively. Following the same mixing and drying process as in Example 1, five dielectric powders were obtained. Subsequently, multilayer ceramic capacitors were fabricated using the same process as in Example 1. However, in this example, the specific surface area of ​​the dielectric powder in the dielectric slurry was 5.0 m² / g, and the highest sintering temperatures of the green body were 1190°C, 1220°C, and 1250°C.

[0091] (2) To evaluate the above 5 dielectric powders, 3 green body sintering temperatures were used to obtain samples 22 to 36. The test items and methods were the same as in Example 1.

[0092] (3) Evaluation results Tables 4 to 6 record the sintering results of samples 22 to 36 under three conditions of sintering temperature 1190℃, 1220℃ and 1250℃. SEM images and EDS analysis diagrams of representative segregated particles in this preparation example are shown in Figures 7 and 8.

[0093] Table 4: Sintering temperature, ZrO2 addition ratio of dielectric powder (MoR ratio), length of segregated particles (i.e., upper and lower limits), highest concentration of segregated particles, second highest concentration of segregated particles, percentage of total length of segregated particles in direct contact with the internal electrode layer, capacitance, and number of deteriorations for samples 22 to 26 (i.e., Comparative Example 5 and Examples 18 to 21). Sample number Dielectric powder Sintering temperature: 1190℃ ZrO2 addition ratio (Morbies) Segregated particles capacitance (μF) Deterioration quantity length (μm) Highest concentration of ingredients Second highest concentration of components The percentage of the total length in direct contact with the internal electrode layer (%) twenty two Comparative Example 5 0.01 Unbiased particles Si Mg N / A 9.3 4 / 40 twenty three Example 18 0.05 0.1~0.5 Si Mg 93 9.9 0 / 40 twenty four Example 19 0.10 0.1~1.0 Si Mg 95 10.3 0 / 40 25 Example 20 0.30 0.5~2.1 Si Mg 95 10.4 0 / 40 26 Example 21 0.50 0.9~2.5 Si Mg 97 10.6 0 / 40

[0094] Table 5: Sintering temperature, ZrO2 addition ratio (MoR ratio) of dielectric powder, length of segregated particles (i.e., upper and lower limits), highest concentration of segregated particles, second highest concentration of segregated particles, total percentage of segregated particles in direct contact with the internal electrode layer, capacitance and number of deteriorations for samples 27 to 31 (i.e., Examples 22 to 26). Sample number Dielectric powder Sintering temperature: 1220℃ ZrO2 addition ratio (Morbies) Segregated particles capacitance (μF) Deterioration quantity length (μm) Highest concentration of ingredients Second highest concentration of components The percentage of the total length in direct contact with the internal electrode layer (%) 27 Example 22 0.01 0.4~0.8 Si Mg 93 10.4 0 / 40 28 Example 23 0.05 0.8~1.9 Si Mg 95 10.4 0 / 40 29 Example 24 0.10 1.2~2.6 Si Mg 96 10.7 0 / 40 30 Example 25 0.30 2.4~4.2 Si Mg 96 10.8 0 / 40 31 Example 26 0.50 2.9~4.8 Si Mg 97 10.9 0 / 40

[0095] Table 6: Sintering temperature of samples 32 to 36 (i.e., Examples 27 to 31), ZrO2 addition ratio of dielectric powder (MoR ratio), length of segregated particles (i.e., upper and lower limits), highest concentration of segregated particles, second highest concentration of segregated particles, total percentage of segregated particles in direct contact with the internal electrode layer, capacitance, and number of deteriorations. Sample number Dielectric powder Sintering temperature: 1250℃ ZrO2 addition ratio (Morbies) Segregated particles capacitance (μF) Deterioration quantity length (μm) Highest concentration of ingredients Second highest concentration of components The percentage of the total length in direct contact with the internal electrode layer (%) 32 Example 27 0.01 0.9~1.8 Si Mg 94 10.4 0 / 40 33 Example 28 0.05 1.2~2.0 Si Mg 96 10.7 0 / 40 34 Example 29 0.10 1.5~2.8 Si Mg 97 10.9 0 / 40 35 Example 30 0.30 2.7~4.8 Si Mg 97 10.9 0 / 40 36 Example 31 0.50 3.9~5.4 Si Mg 97 11.1 0 / 40

[0096] As shown in Table 4, when the sintering temperature is 1190℃ and the ZrO2 addition ratio is 0.01 mol, sample 22 did not form segregated particles due to insufficient sintering, thus becoming Comparative Example 5. However, samples 23 to 26 were able to form segregated particles. Therefore, adding ZrO2 can achieve the effect of lowering the sintering temperature to promote the formation of segregated particles. Therefore, in order to maintain high capacitance while avoiding insulation degradation, ZrO2 can be added appropriately according to the sintering temperature required by the process. For example, when the maximum sintering temperature is 1190℃, the addition ratio of ZrO2 can be set to 0.05 mol to 0.50 mol.

[0097] Thus, ZrO2 can promote the sintering of main component particles and generate segregated particles at low temperature, which can avoid insulation degradation during high-temperature load testing.

[0098] Furthermore, as shown in Tables 4 to 6, the capacitance gradually increases with the formation of segregated particles and the increase in the size of the segregated particles. As shown in Table 4 for sample 22 (i.e., Comparative Example 5), the absence of segregated particles leads to a deterioration in insulation resistance. Since the size of the segregated particles increases with the increase in the proportion of ZrO2 added, ZrO2 can be appropriately added according to the required capacitance within a range where the size of the segregated particles does not exceed 10 micrometers. In this embodiment, the size of the segregated particles is preferably 0.1 micrometers or more and 10 micrometers or less.

[0099] Furthermore, as shown in Tables 4 to 6, the total length in direct contact with the internal electrode layer accounts for more than 90%, and as shown in Figures 7 and 8, segregated particles exist at the interface between the discontinuous portion or the effective electrode portion and the dielectric layer, or segregated particles exist in the discontinuous portion. Furthermore, the segregated particles can be flat, amorphous, or spherical.

[0100] Furthermore, as shown in Figure 8, among the complex segregated particles, there are segregated particles in which different elements were detected, and these segregated particles are composite oxides. This confirms the existence of composite oxides and that the complex discontinuity exists in a discontinuous portion completely occupied by segregated particles.

[0101] Furthermore, high concentrations of Si and Mg were detected in the segregated particles, and relatively low concentrations of composite oxides of Ca and Dy were also detected in the same location. This confirms that the first segregated particles contain composite oxides with Si and Mg as the main components, and in particular, composite oxides containing Si, Mg, Ca and Dy are present.

[0102] In summary, it has been confirmed that the size of the segregated particles is less than 10 micrometers, the segregated particles contain composite oxides with Si and Mg as the main components, the discontinuous part includes the part completely occupied by the segregated particles, the total length in direct contact with the internal electrode layer accounts for more than 90%, and the segregated particles directly in contact with the internal electrode layer exist at the interface between the discontinuous part or the effective electrode part and the dielectric layer. Therefore, the multilayer ceramic capacitor of the present invention has the effect of maintaining high capacitance while further improving the high temperature load life.

[0103] Furthermore, in addition to the composite oxide, the segregated particles also contain small amounts of single oxides such as SiO2, MgO, CaO, and Dy2O3. However, in this embodiment, due to the low proportion of added MnO and ZrO2, MnO and ZrO2 were not detected in the segregated particles.

[0104] It should be noted that when the dielectric paste of this embodiment is mixed with ZrO2 balls, if old ZrO2 balls are used, the ZrO2 component may be mixed into the dielectric powder. The addition ratio of ZrO2 powder can be adjusted according to the required proportion of dielectric powder, or no ZrO2 powder can be added. [Simplified Explanation of the Diagram]

[0028] Figure 1 is a cross-sectional view of the multilayer ceramic capacitor of the present invention along the stacking direction. Figure 2 is an enlarged view showing the observation area A of the effective capacitance portion in Figure 1. Figure 3 is a SEM image of a representative segregated particle in Preparation Example 1 of the present invention. Figure 4 is an EDS analysis diagram of a representative segregated particle in Preparation Example 1 of the present invention. Figure 5 is a schematic diagram of the length calculation of the segregated particles of the present invention. Figure 6 is an enlarged view of the observation area B in Figure 2. Figure 7 is a SEM image of a representative segregated particle in Preparation Example 2 of the present invention. Figure 8 is an EDS analysis diagram of a representative segregated particle in Preparation Example 2 of the present invention.

Claims

1. A multilayer ceramic capacitor, comprising: a capacitor body, which includes: a plurality of alternating stacked dielectric layers and a plurality of internal electrode layers; wherein, The region where the dielectric layer and the internal electrode layer are stacked alternately is defined as an effective capacity region; complex segregated particles, with a size of less than 10 micrometers, are present in the effective capacity region; wherein most of the complex segregated particles are in direct contact with the internal electrode layer, and the composition of the complex segregated particles includes any or a combination of silicon, alkaline earth metals, and rare earth elements, and the concentration of the complex segregated particles containing silicon is greater than the concentration of the complex segregated particles containing alkaline earth metals, and the concentration of the complex segregated particles containing alkaline earth metals is greater than the concentration of the complex segregated particles containing rare earth elements; and two external electrodes, which are respectively disposed at both ends of the capacitor body and are each electrically connected to the internal electrode layer.

2. The multilayer ceramic capacitor as claimed in claim 1, wherein the alkaline earth metal comprises either or a combination of magnesium and calcium.

3. The multilayer ceramic capacitor as claimed in claim 2, wherein the alkaline earth metal comprises magnesium and calcium, and the concentration of the complex segregated particles comprising magnesium is greater than the concentration of the complex segregated particles comprising calcium.

4. The multilayer ceramic capacitor as described in claim 1, wherein the rare earth element comprises dysprosium.

5. The multilayer ceramic capacitor as described in any one of claims 1 to 4, wherein the size of the complex segregated particles is from 0.1 micrometers to 10 micrometers.

6. A multilayer ceramic capacitor as claimed in any one of claims 1 to 4, wherein the shape of the complex segregated particles includes any or a combination of flat, amorphous, and spherical shapes.

7. A multilayer ceramic capacitor as described in any one of claims 1 to 4, wherein the segregated particles comprise composite oxides and single oxides; wherein, The composite oxide contains at least two elements selected from silicon, magnesium, calcium, and dysprosium, and the single oxide contains silicon, magnesium, calcium, dysprosium, or manganese.

8. A multilayer ceramic capacitor as claimed in any one of claims 1 to 4, wherein the multilayer ceramic capacitor has a stacking direction, a length direction and a width direction perpendicular to each other, and the total length of the segregated particles in direct contact with the inner electrode layer is more than 90%, based on the sum of the lengths of all the segregated particles along the length direction.