BME high-capacity multilayer ceramic dielectric capacitor, rare-earth-free dielectric ceramic powder for BME high-capacity multilayer ceramic dielectric capacitor and preparation method of rare-earth-free dielectric ceramic powder

Abstract

The invention relates to a BME high-capacity multilayer ceramic dielectric capacitor, rare earth-free dielectric ceramic powder for the BME high-capacity multilayer ceramic dielectric capacitor and a preparation method of the rare earth-free dielectric ceramic powder, and the dielectric ceramic powder is composed of barium titanate, magnesium oxide or carbonate, manganese oxide or carbonate, calcium carbonate or oxalate, strontium carbonate or oxalate, vanadium pentoxide, silicon dioxide and zirconium oxide in proportion. The limited dielectric ceramic powder does not contain rare earth components, and the cost of raw materials is low; in the prior art, rare earth is used as an important auxiliary component for doping in most of high-K-value formulas, so that on one hand, capturing of oxygen vacancies is facilitated, and the service life of the MLCC is prolonged; on the other hand, the rare earth elements are beneficial to adjusting the capacitance-temperature change curve of the MLCC; according to the invention, calcium element, manganese element and strontium element in a proper proportion are used as auxiliary components to be combined to capture movable oxygen vacancies, so that the insulation resistance and the service life of the MLCC prepared from the dielectric ceramic powder are improved; and meanwhile, the vanadium element is used for adjusting the capacitance-temperature change curve of the MLCC, so that the MLCC meets the X5R characteristic.

Description

Technical Field

[0001] The invention belongs to the field of capacitor preparation, and specifically relates to a BME high-capacitance multilayer ceramic capacitor and rare-earth-free dielectric ceramic powder used therefor, and a preparation method thereof. Background Art

[0002] Multilayer ceramic capacitors (MLCC) have been widely used in communications, automobiles, military and other fields due to their ultra-high power density characteristics. According to market statistics, in 2023, MLCCs of different models and specifications will increase in price, and the price increase of high-capacitance products will be between 20% and 40%.

[0003] The cost of MLCC mainly comes from various raw materials, among which ceramic powder materials are the key raw materials of MLCC. In high-capacitance MLCC, dielectric ceramic powder accounts for as much as 35-45%. The price of rare earth accounts for about 10% of the dielectric ceramic powder. Rare earth-free dielectric ceramic powder can reduce the manufacturing cost of MLCC on the one hand, and reduce the impact of rare earth development on the environment on the other.

[0004] CN116239378A proposed a low-cost, low-loss and temperature-stable dielectric material and preparation method, in which only yttrium oxide was used for rare earth doping, and the dielectric constant was greater than 1210 at room temperature; CN113582683A and CN103964842B disclosed rare earth-free dielectric porcelain powder for MLCC, with a dielectric constant greater than 650, low cost and environmental protection. However, the above-mentioned patents are difficult to achieve large capacity due to their low dielectric constant.

[0005] MLCC is developing towards thinner dielectric layers, which requires ceramic dielectric materials that can ensure the reliability of MLCC even with thinner layers. Dielectric ceramic powder with high dielectric constant and high insulation resistance performance is the key to developing thin-layer, high-capacitance MLCC. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a BME high-capacitance multilayer ceramic capacitor and a rare-earth-free dielectric ceramic powder used therein and a preparation method thereof.

[0007] The present invention adopts the following technical solution: A rare earth-free dielectric porcelain powder for BME high-capacitance multilayer ceramic capacitors is composed of barium titanate, magnesium oxide or carbonate, manganese oxide or carbonate, calcium carbonate or oxalate, strontium carbonate or oxalate, vanadium pentoxide, silicon dioxide, and zirconium oxide in a molar ratio of 100:2.5-5:0.1-0.3:0.03-0.2:0.2-0.7:0.02-0.1:0.2-1.0:0.2-0.6.

[0008] Furthermore, the magnesium oxide or carbonate is nano magnesium oxide or nano magnesium carbonate.

[0009] Furthermore, the manganese oxide or carbonate is nano manganese dioxide, nano manganese tetraoxide or nano manganese carbonate.

[0010] Furthermore, the calcium carbonate or oxalate is nano calcium carbonate or nano calcium oxalate.

[0011] Furthermore, the carbonate or oxalate of strontium is nano-strontium carbonate or nano-strontium oxalate.

[0012] Furthermore, the particle size of the barium titanate is 200-300 nm, and the particle sizes of the magnesium oxide or carbonate, manganese oxide or carbonate, calcium carbonate or oxalate, strontium carbonate or oxalate, vanadium pentoxide, silicon dioxide, and zirconium oxide are all below 200 nm.

[0013] Furthermore, a method for preparing rare earth-free dielectric porcelain powder for BME high-capacitance multilayer ceramic capacitors is as follows: weigh each raw material according to the required weight and mix them evenly by ball milling, then calcine the mixture at 900-1000°C for 0-2h, and obtain the dielectric porcelain powder after crushing.

[0014] A BME high-capacitance multilayer ceramic capacitor is formed by stacking and firing dielectric layers, wherein the dielectric layers include a dielectric layer and electrodes printed on the dielectric layers, and the dielectric layers are formed by tape casting of the dielectric ceramic powder according to any one of claims 1 to 6.

[0015] A method for preparing a BME high-capacitance multilayer ceramic capacitor comprises the following steps: Step 1, mixing dielectric porcelain powder with ethanol, toluene, dispersant, PVB resin and dioctyl phthalate in a ratio of 100: (30-35): (30-35): (0.8-1.2): (8-11): (4-5) to obtain a casting slurry; Step 2, casting the slurry into a dielectric layer strip with a thickness of 3-10 μm, then printing a nickel electrode on the dielectric layer to form a dielectric layer, and stacking the dielectric layers in an offset manner, and then subjecting the laminate to water pressing and slicing to manufacture a green sheet; Step 3, degreasing the embryo, the degreasing time is between 30-200 hours, and the nitrogen flow rate is 0-300L / min; Step 4, sintering the degreased green body into a porcelain body in a reducing atmosphere, and then performing a reoxidation treatment; Step 5, ball-milling and chamfering the sintered ceramic body to lead out the electrode, and using copper electrode slurry for terminal attachment, drying and sintering to obtain the BME high-capacitance multilayer ceramic capacitor.

[0016] Furthermore, in step 4, the sintering temperature is 1200-1250°C.

[0017] It can be seen from the above description of the present invention that, compared with the prior art, the present invention has the following beneficial effects: First, the dielectric porcelain powder of the present invention does not contain rare earth components, and the cost of raw materials is relatively low. In the past, most high-K value formulas used rare earth as an important auxiliary component, which, on the one hand, helps to capture oxygen vacancies, thereby increasing the life of MLCC; on the other hand, rare earth elements help to adjust the capacitance-temperature variation curve of MLCC; in the present invention, the auxiliary components use a suitable proportion of calcium, manganese and strontium to capture movable oxygen vacancies, thereby improving the insulation resistance and life of MLCC made of dielectric porcelain powder; at the same time, vanadium is used to adjust the capacitance-temperature variation curve of MLCC to meet the X5R characteristics; Second, the auxiliary component of the present invention uses a higher proportion of magnesium element, which can improve the dielectric constant and insulation resistance of the dielectric porcelain powder. In Table 1 and Table 2, from the comparison of the three data of Example 1, Example 2 and Comparative Example 4, it can be seen that a suitable higher proportion of nano magnesium oxide can improve the K value and high temperature insulation resistance of the formula; Third, the dielectric porcelain powder of the present invention is mixed with a certain proportion of nano zirconium oxide as an auxiliary component to improve the dielectric constant of the dielectric porcelain powder. In Table 1 and Table 2, by comparing Example 1, Example 5 and Comparative Example 9, it can be seen that the addition of a certain amount of nano zirconium oxide can significantly improve the dielectric constant of the formula; Fourth, the overall particle size D50 of the dielectric porcelain powder of the present invention is less than 300nm, and the capacitance-temperature change rate in the operating temperature range of -55°C to 85°C is ≤±15%, which is suitable for miniaturized, high-capacity X5R type MLCC; Fifth, the dielectric porcelain powder system described in the present invention does not contain lead and rare earth, is environmentally friendly, and has good application prospects; at the same time, the preparation process of the present invention is simple and convenient for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a scanning electron microscope image of a cross section of the dielectric layer of Example 1; Figure 2 The capacity-temperature variation data of Examples 1-6 are organized into a TCC graph. DETAILED DESCRIPTION

[0019] The present invention is further described below through specific implementation modes.

[0020] A rare earth-free dielectric porcelain powder for BME high-capacitance multilayer ceramic capacitors is composed of barium titanate, magnesium oxide or carbonate, manganese oxide or carbonate, calcium carbonate or oxalate, strontium carbonate or oxalate, vanadium pentoxide, silicon dioxide, and zirconium oxide in a molar ratio of 100:2.5-5:0.1-0.3:0.03-0.2:0.2-0.7:0.02-0.1:0.2-1.0:0.2-0.6.

[0021] Among them, the oxide or carbonate of magnesium is nano magnesium oxide or nano magnesium carbonate; the oxide or carbonate of manganese is nano manganese dioxide, nano manganese tetraoxide or nano manganese carbonate; the carbonate or oxalate of calcium is nano calcium carbonate or nano calcium oxalate; the carbonate or oxalate of strontium is nano strontium carbonate or nano strontium oxalate.

[0022] The particle size of barium titanate is 200-300nm; the particle sizes of magnesium oxide or carbonate, manganese oxide or carbonate, calcium carbonate or oxalate, strontium carbonate or oxalate, vanadium pentoxide, silicon dioxide, and zirconium oxide are all below 200nm; specifically, the particle size of barium titanate is 200nm; the particle sizes of magnesium oxide or carbonate, manganese oxide or carbonate, calcium carbonate or oxalate, strontium carbonate or oxalate, vanadium pentoxide, and zirconium oxide are all 50-200nm; the particle size of silicon dioxide is 80-100nm.

[0023] The preparation method is as follows: weigh the raw materials according to the required weight and mix them evenly by ball milling, then calcine the mixture at 900-1000°C for 0-2h, and grind it to obtain dielectric porcelain powder.

[0024] A BME high-capacitance multilayer ceramic capacitor is formed by stacking and firing dielectric layers, wherein the dielectric layers include a dielectric layer and electrodes printed on the dielectric layers, wherein the dielectric layers are formed by tape casting of dielectric ceramic powder.

[0025] The preparation method thereof comprises the following steps: Step 1, mixing dielectric porcelain powder with ethanol, toluene, dispersant, PVB resin and dioctyl phthalate in a ratio of 100: (30-35): (30-35): (0.8-1.2): (8-11): (4-5) to obtain a casting slurry; Step 2, casting the slurry into a dielectric layer strip with a thickness of 3-10 μm, then printing a nickel electrode on the dielectric layer to form a dielectric layer, and stacking the dielectric layers in an offset manner, and then subjecting the laminate to water pressing and slicing to manufacture a green sheet; Step 3, degreasing the embryo, the degreasing time is between 30-200 hours, and the nitrogen flow rate is 0-300L / min; Step 4, sintering the degreased green body at a temperature of 1200-1250° C. in a reducing atmosphere into a ceramic body, and then performing a reoxidation treatment; Step 5, ball-milling and chamfering the sintered ceramic body to lead out the electrode, and using copper electrode slurry for terminal attachment, drying and sintering to obtain a BME high-capacitance multilayer ceramic capacitor.

[0026] Example 1 A rare earth-free dielectric porcelain powder for a BME high-capacitance multilayer ceramic capacitor is composed of barium titanate, magnesium oxide, manganese dioxide, calcium carbonate, strontium carbonate, vanadium pentoxide, silicon dioxide and zirconium oxide in a molar ratio of 100:4:0.15:0.18:0.45:0.05:0.67:0.39.

[0027] The particle size of barium titanate is 200nm; the particle sizes of magnesium oxide or carbonate, manganese oxide or carbonate, calcium carbonate or oxalate, strontium carbonate or oxalate, vanadium pentoxide, and zirconium oxide are all 50-200nm; and the particle size of silicon dioxide is 80-100nm.

[0028] The preparation method is as follows: weigh the raw materials according to the required weight and mix them evenly by ball milling, then calcine the mixture at 1000° C. for 1 hour, and grind it to obtain dielectric porcelain powder.

[0029] A BME high-capacitance multilayer ceramic capacitor is formed by stacking and firing dielectric layers, wherein the dielectric layers include a dielectric layer and electrodes printed on the dielectric layers, wherein the dielectric layers are formed by tape casting of dielectric ceramic powder.

[0030] The preparation method thereof comprises the following steps: Step 1, mixing dielectric porcelain powder with ethanol, toluene, dispersant, PVB resin and dioctyl phthalate in a ratio of 100:30:30:0.8:8:4 to obtain a casting slurry; Step 2, casting the slurry into a dielectric layer strip, the dielectric layer thickness is 4 μm, then printing the nickel electrode on the dielectric layer to form a dielectric layer, and stacking the dielectric layers with each other in an offset manner, and then subjecting the laminate to water pressing and slicing to manufacture a green blank; Step 3, degreasing the embryos, the degreasing time is 140 hours, and the nitrogen flow rate is 180L / min; Step 4, sintering the degreased green body into a porcelain body in a reducing atmosphere, and then performing a reoxidation treatment; Step 5, ball-milling and chamfering the sintered ceramic body to lead out the electrode, and using copper electrode slurry for terminal attachment, drying and sintering to obtain a BME high-capacitance multilayer ceramic capacitor.

[0031] Among them, the product specification is 1210, sintered at 1230℃, 0.8% H2 reducing atmosphere, and reoxidized at 30ppm oxygen concentration. The dielectric layer after sintering is dense, and the scanning electron microscope image of the dielectric layer cross section is as follows Figure 1 shown.

[0032] After the copper paste attached to the end is dried at 120°C, the copper electrode is heat treated in a nitrogen protective atmosphere at 885°C.

[0033] The raw material composition and preparation process of Examples 2-5 are basically the same as those of Example 1, except that the ratios of the raw materials are different. The specific parameters are shown in Table 1.

[0034] Example 6, its raw material composition and preparation process are basically the same as those of Example 1, the difference is that the dielectric porcelain powder is not calcined.

[0035] Comparative Examples 1-14, their raw material composition and preparation process are basically the same as those of Example 1, the difference being that the raw material ratios are different. The specific parameters are detailed in Table 1, wherein the difference between the dielectric porcelain powder in Comparative Example 1 and Example 1 is that 0.5% of nano-grade yttrium oxide is added to Comparative Example 1; the main component BaTiO3 in Comparative Example 2 has a particle size D50 of 500nm, and the other components are the same as those in Example 1; the difference between the dielectric porcelain powder in Comparative Example 3 and Example 1 is that the auxiliary components are all replaced with ordinary oxides (non-nanoscale).

[0036] Table 1 Composition table (mol%) The prepared product can be tested for related electrical properties after being placed for 24 hours, wherein the test frequency is 1000 Hz, the voltage is 1 V, and the breakdown voltage boost rate is 20 V / s.

[0037] The capacitance C, dielectric loss DF, insulation resistance IR and breakdown voltage BDV were tested at room temperature of 25°C and humidity of 50-70%. The dielectric constant was then calculated based on the thickness of the dielectric layer, the effective electrode area, the number of dielectric layers and the capacitance.

[0038] The capacitance variation of MLCC with temperature and the insulation resistance IR at 85℃ were tested between -55℃ and 85℃.

[0039] The measured basic electrical performance data are shown in Table 2, where RC represents the product of capacitance C and insulation resistance IR.

[0040] Table 2 Electrical performance test data table The temperature variation data of Examples 1-6 obtained from the test are organized into a TCC curve diagram, as shown in FIG. Figure 2 As shown, the dielectric porcelain powder of the present invention meets the X5R characteristics.

[0041] By comparing Example 1 with Comparative Example 1, it can be seen that under this formulation system, adding rare earth elements does not increase the dielectric constant, but instead causes a decrease in the dielectric constant.

[0042] By comparing Example 1 and Comparative Example 2, it can be seen that under this formulation system, the dielectric porcelain powder made of larger particles of barium titanate does not meet the X5R characteristics.

[0043] By comparing Example 1 and Comparative Example 3, it can be seen that under this formulation system, the auxiliary component should be selected as nano-scale raw materials. When the particle size of the auxiliary component is smaller than that of the main component, it helps to mix the dielectric porcelain powder more evenly, promote the sintering effect, and make it have a larger dielectric constant and higher insulation resistance.

[0044] By comparing Example 1 with Comparative Examples 7-8 and Comparative Examples 11-13, it can be seen that the present invention uses a suitable ratio of calcium, manganese and strontium to capture mobile oxygen vacancies, and the synergistic effect of the three elements can effectively improve the room temperature and high temperature insulation resistance of the dielectric layer.

[0045] By comparing Example 1 with Comparative Examples 10 and 14, it can be seen that the present invention uses a suitable proportion of vanadium elements to adjust the capacitance-temperature variation curve of MLCC. Excessive or insufficient vanadium elements will cause the dielectric porcelain powder to fail to meet the X5R characteristics, and adding excessive vanadium elements will cause the K value of the dielectric porcelain powder to decrease and the insulation resistance to decrease.

[0046] By comparing Example 1 with Comparative Examples 4 to 14, it can be seen that the basic electrical properties of the formulations beyond the technical scope of the present invention are poor, and may even fail to meet the ultra-high dielectric constant and X5R characteristics.

[0047] The overall particle size D50 of the dielectric porcelain powder of the present invention is less than 300nm, and the capacitance-temperature change rate in the operating temperature range of -55°C to 85°C is ≤±15%, which is suitable for miniaturized, high-capacity X5R type MLCC; and the dielectric porcelain powder system does not contain lead and rare earth, is environmentally friendly, and has good application prospects; at the same time, the preparation process of the present invention is simple and convenient for industrial production.

[0048] The above description is only a preferred embodiment of the present invention, and therefore cannot be used to limit the scope of implementation of the present invention. That is, equivalent changes and modifications made according to the application scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A rare earth-free dielectric porcelain powder for BME high-capacitance multilayer ceramic capacitors, characterized in that: It is composed of barium titanate, magnesium oxide or carbonate, manganese oxide or carbonate, calcium carbonate or oxalate, strontium carbonate or oxalate, vanadium pentoxide, silicon dioxide and zirconium oxide in a molar ratio of 100:2.5-5:0.1-0.3:0.03-0.2:0.2-0.7:0.02-0.1:0.2-1.0:0.2-0.

6.

2. The rare earth-free dielectric porcelain powder for BME high-capacitance multilayer ceramic capacitors according to claim 1, characterized in that: The magnesium oxide or carbonate is nano magnesium oxide or nano magnesium carbonate.

3. The rare earth-free dielectric porcelain powder for BME high-capacitance multilayer ceramic capacitors according to claim 1, characterized in that: The manganese oxide or carbonate is nano manganese dioxide, nano manganese tetraoxide or nano manganese carbonate.

4. The rare earth-free dielectric porcelain powder for BME high-capacitance multilayer ceramic capacitors according to claim 1, characterized in that: The calcium carbonate or oxalate is nano calcium carbonate or nano calcium oxalate.

5. The rare earth-free dielectric porcelain powder for BME high-capacitance multilayer ceramic capacitors according to claim 1, characterized in that: The carbonate or oxalate of strontium is nano strontium carbonate or nano strontium oxalate.

6. The rare earth-free dielectric porcelain powder for BME high-capacitance multilayer ceramic capacitors according to claim 1, characterized in that: The particle size of the barium titanate is 200-300nm, and the particle sizes of the magnesium oxide or carbonate, manganese oxide or carbonate, calcium carbonate or oxalate, strontium carbonate or oxalate, vanadium pentoxide, silicon dioxide, and zirconium oxide are all below 200nm.

7. The method for preparing a rare earth-free dielectric porcelain powder for a BME high-capacitance multilayer ceramic capacitor according to claim 1, characterized in that: The details are as follows: each raw material is weighed according to the required weight and mixed evenly by ball milling, and then the mixture is calcined at 900-1000° C. for 0-2 hours, and the dielectric porcelain powder is obtained after being crushed.

8. A BME high capacitance multilayer ceramic capacitor, characterized in that: The dielectric layer is formed by stacking and firing dielectric layers, wherein the dielectric layer comprises a dielectric layer and electrodes printed on the dielectric layer, and the dielectric layer is formed by tape casting of the dielectric porcelain powder according to any one of claims 1 to 6.

9. The method for preparing a BME high-capacitance multilayer ceramic capacitor according to claim 8, characterized in that: The following steps are involved: Step 1, mixing dielectric porcelain powder with ethanol, toluene, dispersant, PVB resin and dioctyl phthalate in a ratio of 100: (30-35): (30-35): (0.8-1.2): (8-11): (4-5) to obtain a casting slurry; Step 2, casting the slurry into a dielectric layer strip with a thickness of 3-10 μm, then printing a nickel electrode on the dielectric layer to form a dielectric layer, and stacking the dielectric layers in an offset manner, and then subjecting the laminate to water pressing and slicing to manufacture a green sheet; Step 3, degreasing the embryo, the degreasing time is between 30-200 hours, and the nitrogen flow rate is 0-300L / min; Step 4, sintering the degreased green body into a porcelain body in a reducing atmosphere, and then performing a reoxidation treatment; Step 5, ball-milling and chamfering the sintered ceramic body to lead out the electrode, and using copper electrode slurry for terminal attachment, drying and sintering to obtain the BME high-capacitance multilayer ceramic capacitor.

10. The method for preparing a BME high-capacitance multilayer ceramic capacitor according to claim 9, characterized in that: In step 4, the sintering temperature is 1200-1250°C.

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