Barium-rich ceramic dielectric material, multilayer ceramic capacitor and preparation method thereof

Abstract

The invention provides a barium-rich ceramic dielectric material, a multilayer ceramic capacitor and a preparation method thereof, and relates to the technical field of ceramic dielectric. The barium-rich ceramic dielectric material comprises the following components in percentage by mass: 97.0-99.5% of a main crystal phase A, a stoichiometric formula of BaxTiO3, 1.000 < = x < = 1.050, 0.2-1% of an auxiliary material B, TiO3 with a stoichiometric formula of (M, Mn), and 0.3-2% of a modified additive, wherein M is one or more of Mg, Ca and Sr. The preparation method comprises the following steps: carrying out step-by-step wet ball milling, calcining to prepare the main crystal phase A and the auxiliary material B, mixing with the modified additive, and carrying out ball milling and drying to obtain the ceramic dielectric material. When a multilayer ceramic capacitor is prepared on the basis of the material, the material, absolute ethyl alcohol and a PVB adhesive are mixed for pulping and film casting, after treatment such as overprinting and isostatic pressing with nickel slurry as an inner electrode, sintering is performed for 1.5-6 hours at the temperature of 1180-1300 DEG C in a reducing atmosphere, and the multilayer ceramic capacitor is prepared. The capacitor is excellent in dielectric property, is adaptive to a cheap metal inner electrode, and meets the X7R characteristic requirement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic dielectric, in particular to a barium-rich ceramic dielectric material, a multilayer ceramic capacitor and a preparation method thereof. BACKGROUND

[0002] The multilayer ceramic capacitor (MLCC) is a capacitor with a structure similar to a monolithic structure, which is formed by stacking ceramic dielectric films with printed electrodes (internal electrodes) in a staggered manner, followed by one-time high-temperature sintering to form a ceramic chip, and finally sealing metal layers (external electrodes) on both ends of the chip. In order to meet the development trend of electronic systems towards miniaturization, large capacity, high reliability and low cost, multilayer ceramic capacitors have the characteristics of large capacity, small size, easy to be sheeted, and their development direction is diversified. At the same time, in order to meet the needs of portable communication tools, multilayer ceramic capacitors are also developing towards low-voltage large-capacity, ultra-small and ultra-thin, and high reliability.

[0003] Therefore, the present application is proposed after the applicant studies the existing technology. SUMMARY

[0004] At present, in combination with the cost demand, the multilayer ceramic capacitor using inexpensive metals such as copper, nickel or their alloys to replace noble metals as internal electrodes has become the mainstream of the market, however, the multilayer ceramic capacitor using copper, nickel or their alloys as internal electrodes must be sintered in a reducing atmosphere. In order to improve the reliability of the multilayer ceramic capacitor, it is necessary to ensure that it has a high insulation resistance value at a high temperature of 125℃.

[0005] Therefore, the present application provides a barium-rich ceramic dielectric material and a preparation method thereof, which has good dispersibility, uniformity, high temperature insulation resistance value and the like. At the same time, the present application also provides a multilayer ceramic capacitor based on the ceramic dielectric material and a preparation method thereof, which has the advantages of simple preparation method, easy operation and suitability for industrial large-scale production. The prepared multilayer ceramic capacitor can be sintered at a relatively wide temperature.

[0006] To solve the above technical problems, the present application provides a barium-rich ceramic dielectric material, which comprises 97.0-99.5% of main crystal phase A, 0.2-1% of auxiliary material B and 0.3-2% of modified additive by mass fraction. The main crystal phase A is prepared according to the stoichiometric formula Ba x TiO3, wherein 1.000≤x≤1.050. The auxiliary material B is prepared according to the stoichiometric formula (M, Mn)TiO3, wherein M is one or more of Mg, Ca and Sr.

[0007] As a further optimization, the modifying additive is composed of two or more of ZrO2, Nb2O5, SiO2, Y2O3, Dy2O3, Er2O3, Ho2O3, and Gd2O3.

[0008] As a further optimization, the mass fraction of each component in the modifying additive ranges from 0.01 to 1.0% for ZrO2, from 0.01 to 1.0% for Nb2O5, from 0.05 to 0.6% for SiO2, from 0.01 to 1.5% for Y2O3, from 0.01 to 1.0% for Dy2O3, from 0.01 to 1.0% for Er2O3, from 0.01 to 1.0% for Ho2O3, and from 0.01 to 1.0% for Gd2O3.

[0009] The application also provides a preparation method of the barium-rich ceramic dielectric material as described above, comprising the following steps: S1: wet ball milling the mixture of barium salt and titanium salt, and then calcining the mixture at 1030-1200°C in an air atmosphere for 2-4 hours to obtain a main crystal phase A; S2: wet ball milling the mixture of M salt, manganese salt, and TiO2, and then calcining the mixture at 1100-1150°C in an air atmosphere for 2-4 hours to obtain an auxiliary material B; S3: wet ball milling the mixture of the main crystal phase A, the auxiliary material B, and the modifying additive, and then drying the mixture to obtain the ceramic dielectric material.

[0010] As a further optimization, in steps S1 and S2, the mixed material is mixed with deionized water at a weight ratio of 1:1-2 and then wet ball milled.

[0011] As a further optimization, in step S3, the mixed material is mixed with deionized water at a weight ratio of 1:0.6-1 and then wet ball milled.

[0012] The application also provides a preparation method of a multilayer ceramic capacitor, comprising the following steps: mixing the ceramic dielectric material with anhydrous ethanol and a binder, ball milling to form a slurry, and then flow casting to obtain a ceramic dielectric film green body; performing overprinting, isostatic pressing, cutting, degassing, sintering, chamfering, and external electrode formation on the ceramic dielectric film green body by using a nickel slurry as an internal electrode to obtain the multilayer ceramic capacitor; and the sintering condition is sintering at 1180-1300°C in a reducing atmosphere for 1.5-6 hours.

[0013] As a further optimization, the binder is a PVB binder.

[0014] As a further optimization, the ceramic dielectric material, the anhydrous ethanol, and the PVB binder are mixed at a mass ratio of 10:(4-6):(3-4.5).

[0015] The application also provides a multilayer ceramic capacitor prepared according to the preparation method of the multilayer ceramic capacitor.

[0016] By adopting the technical scheme, the application can achieve the following technical effects: The application provides a barium-rich ceramic dielectric material, a multilayer ceramic capacitor and a preparation method thereof. The material has excellent and controllable performance. The barium-rich design of the main crystal phase improves the insulation and reduction resistance of the material. The synergistic effect of the modified additives makes the dielectric constant continuously adjustable between 2000 and 3600. The insulation resistance at 125 DEG C is greater than 1*10 5 M, the working voltage is greater than 50 V, the capacitance temperature change rate is between ±15%, the dielectric loss is less than or equal to 1.0%, and the reliability is high. The preparation process is suitable for industrialization. The material ratio, calcination temperature and time of each step are clear, and the process is simple and easy to operate. The average particle size of the material after ball milling is 250-600 nm, and the dispersity and uniformity are good, so that large-scale production can be realized. The product has strong adaptability. The multilayer ceramic capacitor can be sintered in a reducing atmosphere at a wide temperature range of 1180-1300 DEG C, and is well matched with base metals such as nickel, copper or alloys, thereby solving the sintering adaptation problem of traditional cheap metal internal electrodes of MLCC. The cost advantage is significant. The internal electrode does not need to rely on noble metal silver / palladium, and the production cost is reduced by replacing the base metal, while high performance and high reliability are taken into account, which meets the development trend of small size, large capacity and low cost of electronic equipment. DETAILED DESCRIPTION

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the application clearer, the following will combine the embodiments of the application to clearly and completely describe the technical solutions in the embodiments of the application. Obviously, the described embodiments are some of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the application. Therefore, the following detailed description of the embodiments of the application is not intended to limit the scope of the claimed application, but only represents selected embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the application.

[0018] The application provides a high-frequency barium-rich ceramic dielectric material for a multilayer ceramic capacitor suitable for a reducing atmosphere and low-temperature sintering. The ceramic dielectric material contains, by mass fraction, 97.0-99.5% of a main crystal phase A, 0.2-1% of an auxiliary material B, and 0.3-2% of a modified additive. The main crystal phase A is Bax TiO3 is used as the raw material, wherein 1.000≤x≤1.050; the auxiliary material B is used as the raw material according to the stoichiometric formula (M,Mn)TiO3, wherein M is one or more of Mg, Ca, and Sr.

[0019] Preferably, the modified additive is composed of two or more of ZrO2, Nb2O5, SiO2, Y2O3, Dy2O3, Er2O3, Ho2O3, and Gd2O3.

[0020] Among them, the barium-rich design in the main crystal A material can improve the insulation of the material, obtain a wide temperature sintering range, and the dielectric constant can be continuously adjusted from 2000 to 3600.

[0021] Preferably, the mass fraction range of each component in the modified additive is: ZrO2 0.01~1.0%, Nb2O5 0.01~1.0%, SiO2 0.05~0.6%, Y2O3 0.01~1.5%, Dy2O3 0.01~1.0%, Er2O3 0.01~1.0%, Ho2O3 0.01~1.0%, and Gd2O3 0.01~1.0%.

[0022] By optimizing the selection and proportion of modifying additives, the performance of ceramic dielectric materials can be further improved, resulting in multilayer ceramic capacitors with superior performance, such as further reducing dielectric loss.

[0023] The present invention also provides a method for preparing the barium-rich ceramic dielectric material as described above, comprising the following steps: S1: After wet ball milling the mixture of barium salt and titanium salt, the mixture is calcined at 1030℃~1200℃ for 2~4h in air atmosphere to obtain the main crystalline phase A; S2: The mixture of M salt, manganese salt and TiO2 is wet ball-milled and then calcined at 1100℃~1150℃ for 2~4h in air atmosphere to obtain auxiliary material B, wherein M is one or more of Mg, Ca and Sr; S3: The material after mixing the main crystalline phase A, auxiliary material B and modified additives is subjected to wet ball milling and dried to obtain ceramic media material.

[0024] Furthermore, in steps S1 and S2 respectively, the mixed materials are mixed with deionized water at a weight ratio of 1:1~2 and then wet ball milled.

[0025] Furthermore, in step S3, the mixed material is mixed with deionized water at a weight ratio of 1:0.6~1 and then wet ball milled.

[0026] In a preferred embodiment, in step S3, adding a surfactant with a mass fraction of 2-5% of the mixture during wet ball milling can effectively increase the ball milling effect and improve the uniformity and stability of the material. Details will not be elaborated further.

[0027] In step S3, the mixture is ball-milled until the average particle size reaches 250–600 nm. After ball milling, it is dried using a spray drying tower or other methods.

[0028] This invention also provides a method for preparing a multilayer ceramic capacitor, comprising the following steps: mixing ceramic dielectric material with anhydrous ethanol and PVB binder, ball milling to form a slurry, obtaining a ceramic dielectric film green body by casting, using nickel paste as the inner electrode for overlay printing, isostatic pressing, cutting, debinding, sintering, chamfering, and terminating with copper or copper alloy external electrodes to obtain a multilayer ceramic capacitor, wherein the sintering conditions are: sintering at 1180~1300℃ in a reducing atmosphere and holding at that temperature for 1.5~6 hours.

[0029] The ceramic medium material, anhydrous ethanol and PVB adhesive are mixed in a mass ratio of 10:(4~6):(3~4.5).

[0030] The dielectric constant of the obtained multilayer ceramic capacitor is 2000-3600, and its characteristics meet the requirements of X7R. It can be well matched with inexpensive metal internal electrodes.

[0031] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0032] Example (1) High-purity barium carbonate and titanium dioxide were placed in a ball mill according to the composition ratio in Table 1 and wet ball milled. After being mixed evenly and dried, they were calcined in an air furnace at 1080℃, 1130℃ and 1180℃ for 3 hours respectively to synthesize Ba. x TiO3 is the main crystalline phase, where 1.000≤x≤1.050.

[0033] (2) High-purity magnesium carbonate, manganese carbonate, calcium carbonate and titanium dioxide were placed in a ball mill according to the composition ratio in Table 2 and wet ball milled. After being mixed evenly and dried, the mixture was calcined in an air furnace at 1120°C for 3 hours to synthesize auxiliary material (M,Mn)TiO3.

[0034] (3) According to the composition ratio in Table 3, add Ba xThe TiO3 main crystalline phase, auxiliary materials, and various modifying additives are weighed according to the weight ratio of the formula and placed in a ball mill. Deionized water is added at a weight ratio of 1:0.8 (mixture:deionized water) for wet ball milling, ensuring uniform mixing so that the average particle size of the milled powder reaches 250-600 nm. After milling, the powder is dried in a spray drying tower to obtain powdered ceramic media material.

[0035] (4) Preparation of multilayer ceramic capacitor samples: Take the ceramic dielectric material obtained by the above method, and according to the proportion, add 40-60g of anhydrous ethanol and 30-45g of PVB binder to 100g of ceramic dielectric material powder, ball mill to form a slurry, and obtain a ceramic dielectric film green blank with a thickness of 15 micrometers by casting. Then, use nickel paste as the inner electrode for overprinting, isostatic pressing, cutting, glue removal, sintering, chamfering, and end copper or copper alloy external electrodes to obtain a multilayer ceramic capacitor. The sintering conditions are: sintering at a temperature of 1180-1300℃ in a reducing atmosphere furnace and holding for 1.5-6 hours.

[0036] Table 1 Ba x Formulation table of TiO3 main crystal phase

[0037] Table 2 Formulation of (M,Mn)TiO3 auxiliary materials

[0038] Table 3 Formulation table of ceramic media composition

[0039] Table 4. Dielectric property test results

[0040] In summary, as shown in Table 4, the nickel internal electrode multilayer ceramic capacitors manufactured through the above process, using ceramic dielectric materials with good resistance to reduction, can achieve room temperature dielectric constants between 2000 and 3600 and insulation resistance values ​​greater than 1*10⁻⁶ at 125℃ by adjusting the proportions of different raw materials within a temperature range of 1180℃ to 1300℃. 5 A continuously adjustable dielectric ceramic material with MΩ, operating voltage > 50V, capacitance temperature variation rate between +15% and -15%, and room temperature dielectric loss ≤ 1.0%. Replacing precious metals silver / palladium electrodes with inexpensive metals such as nickel, copper, or their alloys reduces production costs. Simultaneously, the high dielectric properties meet the reduction resistance requirements of X7R temperature-dependent ceramic capacitors.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A barium-rich ceramic dielectric material, characterized in that, By mass fraction, it comprises 97.0–99.5% main crystalline phase A, 0.2–1% auxiliary material B, and 0.3–2% modifying additives; The main crystalline phase A is stoichiometric according to the chemical formula Ba x TiO3 is used as the ingredient, wherein 1.000≤x≤1.050; The auxiliary material B is prepared according to the stoichiometric formula (M,Mn)TiO3, wherein M is one or more of Mg, Ca, and Sr.

2. The barium-rich ceramic dielectric material according to claim 1, characterized in that... The modified additive is composed of two or more of ZrO2, Nb2O5, SiO2, Y2O3, Dy2O3, Er2O3, Ho2O3, and Gd2O3.

3. The barium-rich ceramic dielectric material according to claim 2, characterized in that... The mass fraction range of each component in the modified additive is as follows: ZrO2 0.01~1.0%, Nb2O5 0.01~1.0%, SiO2 0.05~0.6%, Y2O3 0.01~1.5%, Dy2O3 0.01~1.0%, Er2O3 0.01~1.0%, Ho2O3 0.01~1.0%, and Gd2O3 0.01~1.0%.

4. A method for preparing a barium-rich ceramic dielectric material as described in any one of claims 1 to 3, characterized in that... This includes the following steps: S1: After wet ball milling the mixture of barium salt and titanium salt, the mixture is calcined at 1030℃~1200℃ for 2~4h in air atmosphere to obtain the main crystalline phase A; S2: The mixture of M salt, manganese salt and TiO2 is wet ball-milled and then calcined at 1100℃~1150℃ for 2~4h in air atmosphere to obtain auxiliary material B; S3: The material after mixing the main crystalline phase A, auxiliary material B and modified additives is subjected to wet ball milling and dried to obtain ceramic media material.

5. The method for preparing barium-rich ceramic dielectric material according to claim 4, characterized in that... In steps S1 and S2, the mixed materials are mixed with deionized water at a weight ratio of 1:1 to 2 and then wet ball milled.

6. The method for preparing barium-rich ceramic dielectric material according to claim 4, characterized in that... In step S3, the mixed material is mixed with deionized water at a weight ratio of 1:0.6~1 and then wet ball milled.

7. A method for preparing a multilayer ceramic capacitor, characterized in that... The process includes the following steps: mixing the ceramic dielectric material prepared according to any one of claims 4 to 6 with anhydrous ethanol and a binder, ball milling to form a slurry, casting to obtain a ceramic dielectric film green body, using nickel paste as the inner electrode for overlay printing, isostatic pressing, cutting, debinding, sintering, chamfering, and terminating with copper or copper alloy external electrodes to obtain a multilayer ceramic capacitor, wherein the sintering conditions are: sintering at 1180 to 1300°C in a reducing atmosphere and holding for 1.5 to 6 hours.

8. The method for preparing a multilayer ceramic capacitor according to claim 7, characterized in that... The adhesive is a PVB adhesive.

9. The method for preparing a multilayer ceramic capacitor according to claim 8, characterized in that... Ceramic media material, anhydrous ethanol and PVB adhesive are mixed in a mass ratio of 10:(4~6):(3~4.5).

10. A multilayer ceramic capacitor, characterized in that... It is prepared by the method according to any one of claims 7 to 9.

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