Multilayer chip ceramic capacitor and method for manufacturing the same

Abstract

The application discloses a multilayer chip ceramic capacitor and a preparation method thereof, and relates to the technical field of ceramic capacitors. The multilayer chip ceramic capacitor comprises a silicon substrate layer, a dielectric ceramic layer, an internal electrode layer and an end electrode. The end electrode is arranged above the silicon substrate layer, and the internal electrode layer is arranged below the end electrode. The dielectric ceramic layer is arranged between the internal electrode layers. The dielectric ceramic layer is made of a nano-level barium titanate plate, and the barium titanate plate is doped with lanthanum oxide, strontium oxide and calcium oxide. The internal electrode layer is made of nickel particles and coated with rare earth oxides to reduce oxidation. The end electrode comprises a first corrosion-resistant layer, a second corrosion-resistant layer and a third corrosion-resistant layer. The third corrosion-resistant layer is fixedly connected to the top end of the silicon substrate layer. The second corrosion-resistant layer is arranged at the top end of the first corrosion-resistant layer. The third corrosion-resistant layer is arranged at the top end of the second corrosion-resistant layer. The end electrode can prevent metal migration during long-term use, and the contact effect is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic capacitors, and in particular to a multilayer chip ceramic capacitor and a preparation method thereof. Background Art

[0002] Multilayer ceramic capacitors (MLCCs), as an important electronic component, are widely used in electronic circuits, particularly in consumer electronics, communications, automotive electronics, and industrial control. Their core characteristics are high capacity, high reliability, and miniaturization, providing high stability and high-frequency characteristics. As modern electronic devices continue to demand higher frequencies, lower losses, and higher densities, the performance of MLCCs is also constantly improving to meet these demands.

[0003] In existing technologies, terminal electrodes usually adopt a Ni / Sn double-layer structure. Although this structure is easy to implement during the manufacturing process, due to the oxidizing properties of nickel and the softening properties of tin, it may cause electrode failure during long-term use, affecting the stability and reliability of the capacitor. Summary of the Invention

[0004] The object of the present invention is to provide a multilayer chip ceramic capacitor and a preparation method thereof, which solves the problem that metal migration easily occurs in the terminal electrodes during long-term use, resulting in poor contact or welding.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] A multilayer chip ceramic capacitor and a method for manufacturing the same, comprising: a silicon base layer, a dielectric ceramic layer, an internal electrode layer, and a terminal electrode, wherein a pair of terminal electrodes are disposed above the silicon base layer, a plurality of internal electrode layers are disposed between the pair of terminal electrodes, and a dielectric ceramic layer is disposed between the plurality of internal electrode layers;

[0007] The dielectric ceramic layer includes a nano-scale barium titanate plate doped with lanthanum oxide, strontium oxide, and calcium oxide;

[0008] The internal electrode layer is made of nickel particles and coated with rare earth oxide;

[0009] The terminal electrode includes: a first anti-corrosion layer, a second anti-corrosion layer and a third anti-corrosion layer. The second anti-corrosion layer is arranged on the top of the first anti-corrosion layer, and the third anti-corrosion layer is arranged on the top of the second anti-corrosion layer. The first anti-corrosion layer is a tin layer, and the second anti-corrosion layer is a silver layer, which covers the surface of the nickel particle layer. The third anti-corrosion layer is a conductive layer composed of nickel particles. The particle size of the nickel particles in the internal electrode layer is 10 nanometers to 500 nanometers.

[0010] Preferably, the second anti-corrosion layer is an electroplating layer with a thickness of 0.1 μm to 2 μm.

[0011] A method for preparing a multilayer chip ceramic capacitor, for preparing the multilayer chip ceramic capacitor as described above, comprising:

[0012] Step S1: mixing barium titanate plate powder with an appropriate amount of organic solvent, dispersant and binder, and performing ball milling or ultrasonic dispersion to ensure uniform dispersion of the powder and obtain a stable ceramic slurry;

[0013] Step S2: Select appropriate nickel powder and mix it with a proper amount of binder and solvent to form an internal electrode slurry;

[0014] Step S3, uniformly coating the prepared ceramic slurry on the carrier film by a tape casting method to form a film layer;

[0015] Step S4: After drying, the film layer is cut into suitable sizes to obtain a plurality of dielectric ceramic sheets;

[0016] Step S5: Print the prepared inner electrode slurry on the ceramic film, usually between alternating layers of the ceramic film, and print a layer of electrode on each layer of the ceramic film to form a multi-layer structure.

[0017] Preferably, in step S6, multiple layers of ceramic sheets are stacked together, and the electrode layer and the ceramic layer are ensured to perfectly overlap;

[0018] Step S7: pressing the stacked layers using heat pressing or mechanical pressure;

[0019] Step S8, placing the laminated multilayer sheet structure into a high-temperature sintering furnace for sintering;

[0020] Step S9: coating terminal electrodes at both ends of the sintered multilayer ceramic capacitor, typically using a three-layer structure of silver / nickel / tin, to form a first anti-corrosion layer, a second anti-corrosion layer, and a third anti-corrosion layer.

[0021] Preferably, in step S10, the capacitor is packaged.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] When using the capacitor, the terminal electrode is connected to the external power supply to energize the capacitor. Under the action of voltage, the charge passes through the first anti-corrosion layer of the terminal electrode from the external circuit, so that the first anti-corrosion layer conducts through the nickel particles into the second anti-corrosion layer, and then passes through the second anti-corrosion layer to improve conductivity and enter the third anti-corrosion layer, so that the charge stably enters one end of the capacitor through the third anti-corrosion layer. Negative charge accumulates on an inner electrode layer, and positive charge accumulates on the inner electrode layer opposite to it. Due to the electrical insulation of the ceramic layer, an electric field is established between the inner electrode layer and the outer electrode layer through the dielectric ceramic layer. As the charge accumulates, the intensity of the electric field gradually increases, and the stored energy also increases accordingly, which solves the problem of metal migration of the terminal electrode during long-term use, resulting in poor contact or welding problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] The structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not intended to limit the conditions under which the present invention can be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportional relationships, or adjustments in size should still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and objectives that can be achieved by the present invention.

[0026] Figure 1 It is a schematic diagram of the overall structure of a multilayer chip ceramic capacitor;

[0027] Figure 2 The figure is a schematic structural diagram of the terminal electrodes of a multilayer ceramic capacitor.

[0028] Illustration:

[0029] 1. Silicon base layer; 2. Dielectric ceramic layer; 3. Internal electrode layer; 4. Terminal electrode; 401. First anti-corrosion layer; 402. Second anti-corrosion layer; 403. Third anti-corrosion layer; DETAILED DESCRIPTION

[0030] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally located component.

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0033] Multilayer ceramic capacitors are a special type of ceramic capacitor. They are composed of multiple layers of thin film structures, each of which has a dielectric function and is electrically connected to the terminal electrodes through the inner electrode layer. Through the multilayer design, ceramic capacitors can achieve a larger capacitance and are compact, making them very suitable for applications where space is limited but high performance is required. Ceramic capacitors are an important electronic component widely used in various electronic devices. Their main function is to store charge and store and release energy in the circuit, helping to stabilize current and voltage, especially in high-frequency circuits.

[0034] refer to Figure 1 - Figure 2 As shown, an embodiment of the present invention provides a multilayer chip ceramic capacitor, comprising: a silicon base layer 1, a dielectric ceramic layer 2, an internal electrode layer 3 and a terminal electrode 4, wherein a pair of terminal electrodes 4 are provided above the silicon base layer 1, a plurality of internal electrode layers 3 are provided between the pair of terminal electrodes 4, and a dielectric ceramic layer 2 is provided between the plurality of internal electrode layers 3;

[0035] The dielectric ceramic layer 2 comprises a nano-scale barium titanate plate doped with lanthanum oxide, strontium oxide and calcium oxide;

[0036] The internal electrode layer 3 is made of nickel particles and coated with rare earth oxide to reduce oxidation;

[0037] The terminal electrode 4 includes a first anti-corrosion layer 401 , a second anti-corrosion layer 402 and a third anti-corrosion layer 403 . The second anti-corrosion layer 402 is disposed on top of the first anti-corrosion layer, and the third anti-corrosion layer 403 is disposed on top of the second anti-corrosion layer 402 .

[0038] The silicon substrate layer 1 supports the entire capacitor; the dielectric ceramic layer 2 is primarily responsible for charge storage and electric field isolation; the internal electrode layer 3 provides a current conduction path and helps form an electric field to achieve the capacitance effect; the terminal electrode 4 connects the capacitor to the external circuit, providing welding reliability and electrical connectivity.

[0039] An external power source is electrically connected to the terminal electrode 4, allowing charges to pass from the external circuit through the first anti-corrosion layer 401 of the terminal electrode 4. The first anti-corrosion layer 401 conducts electricity through the nickel particles and enters the second anti-corrosion layer 402. The charges then pass through the second anti-corrosion layer 402 to improve conductivity and enter the third anti-corrosion layer 403. The charges then stably enter one end of the capacitor through the third anti-corrosion layer 403. Negative charges accumulate on one inner electrode layer, while positive charges accumulate on the opposite inner electrode layer. As the charges accumulate, the strength of the electric field gradually increases, and the stored energy also increases accordingly.

[0040] When using the capacitor, the charge passes through the first anti-corrosion layer 401 of the terminal electrode 4, and then the charge passes from the first anti-corrosion layer 401 through the second anti-corrosion layer 402 into the third anti-corrosion layer 403, so that the negative charge accumulates on one inner electrode layer, and the positive charge accumulates on the opposite inner electrode layer. As the charge accumulates, the intensity of the electric field gradually increases, and the stored energy also increases accordingly, which solves the problem that the terminal electrode is prone to metal migration during long-term use, resulting in poor contact or welding problems.

[0041] As another embodiment, this embodiment further provides a method for preparing a multilayer chip ceramic capacitor, which is used to prepare the multilayer chip ceramic capacitor, comprising:

[0042] Step S1: mixing barium titanate plate powder with an appropriate amount of organic solvent, dispersant and binder, and performing ball milling or ultrasonic dispersion to ensure uniform dispersion of the powder and obtain a stable ceramic slurry;

[0043] Step S2: Select appropriate nickel powder and mix it with a proper amount of binder and solvent to form an internal electrode slurry;

[0044] Step S3, uniformly coating the prepared ceramic slurry on the carrier film by a tape casting method to form a film layer;

[0045] Step S4: After drying, the film layer is cut into suitable sizes to obtain a plurality of dielectric ceramic sheets;

[0046] Step S5, print the prepared inner electrode slurry on the ceramic film, usually between the alternating layers of the ceramic film, and print a layer of electrode on each layer of ceramic film to form a multi-layer structure; first, the stability of the capacitor structure is ensured through a precise preparation process. The method is carried out through a series of steps, including mixing barium titanate powder with other chemical materials to make a ceramic slurry, coating by a cast film method, drying, cutting and printing the inner electrode slurry to form a multi-layer structure of a ceramic capacitor, and finally forming a dense multilayer capacitor by hot pressing and high-temperature sintering. During the preparation process, the particle size of the nickel particles used is controlled between 10 nanometers and 500 nanometers, which not only effectively improves the conductivity of the electrode, but also enhances its antioxidant ability, further improving the stability of the capacitor, especially in an environment with high temperature and large humidity changes. The use of nickel particles of this particle size can significantly improve the durability and long-term stability of the capacitor, prevent the influence of metal migration on the performance of the capacitor, thereby ensuring the capacitor. Service life and reliability; Casting method: At the beginning, it is necessary to prepare a slurry. The slurry is generally composed of solid powder (such as ceramic powder such as barium titanate), organic solvent (such as ethanol), dispersant (such as sodium polyacrylate) and binder (such as polyvinyl alcohol). Ensure that the solid powder is evenly dispersed and maintains good fluidity and stability. The slurry is then applied to a smooth substrate surface (usually a film substrate such as polyester film or metal film) through a uniform scraper or roller device. The applied slurry is dried at an appropriate temperature to evaporate the solvent and form a solid ceramic film. The dried film usually needs to undergo post-processing steps such as hot pressing and sintering to further remove the solvent and improve the density and stability of the ceramic film. For the manufacture of ceramic capacitors, the sintered ceramic film will form a hard and dense ceramic layer.

[0047] First, a barium titanate powder with a weight percentage of 50%–70% is selected, while an organic solvent accounts for 20%–40% by weight, a dispersant typically accounts for 0.5%–2%, and the remainder is a binder. This powder has a high dielectric constant, which provides the required capacitance for the capacitor. The barium titanate powder is then mixed with 20%–40% by weight of an organic solvent (such as ethanol), a dispersant (such as sodium polyacrylate), and a binder (such as polyvinyl alcohol). The mixture is then processed using ball milling or ultrasonic dispersion. Ball milling involves a rotating barrel filled with grinding media (typically steel or ceramic balls). During ball milling, the powder and the balls, under the influence of high-speed rotation, collide, rub, and shear, grinding the powder into smaller particles. Ultrasonic dispersion involves converting ultrasonic waves into high-frequency vibration waves through an ultrasonic generator and transmitting them into the dispersion liquid. When the vibration waves encounter the particles in the liquid, they generate extremely high local temperatures and pressures, forming bubbles. When the bubbles collapse, they generate a strong impact force, causing cracks or ruptures on the particle surface, ultimately achieving a dispersion effect. This ensures that the barium titanate powder is evenly dispersed in the solvent, resulting in a stable ceramic slurry. This slurry will be used in the subsequent coating process to ensure that the ceramic powder is uniform and free of precipitation. Next, a nickel powder with a dosage of 60%–80% (weight ratio) is selected. This powder has good conductivity and is the main component of the inner electrode. Nickel powder is mixed with a binder (such as polyvinyl alcohol) and a solvent (such as ethanol) in an amount of 5%-15% (by weight). By stirring and dispersing, a uniform internal electrode slurry is obtained. The slurry will be applied to the ceramic film in the subsequent printing step to form an internal electrode layer. The prepared ceramic slurry is evenly coated on an appropriate carrier film by the casting method. The casting method is a precise coating technology that can form a uniform ceramic slurry layer on the carrier film. The coated slurry needs to be dried to remove the solvent to make it a dry ceramic film. The dried ceramic film layer is cut into suitable sizes, usually according to the design requirements of the capacitor. Through precise cutting, multiple dielectric ceramic sheets can be obtained. These ceramic sheets will be used for lamination in subsequent steps. The cutting process should ensure that the size of each ceramic sheet is consistent to ensure the stability of the final overall structure of the capacitor. The prepared internal electrode slurry is printed onto the cut ceramic film by screen printing technology. The inner electrode layer is usually printed between alternating layers of ceramic film to ensure good contact and electrical connection between the inner electrode layer and the ceramic layer. A layer of inner electrode is printed on each layer of ceramic film, and then these layers are stacked together to form a multilayer structure. The arrangement between each inner electrode layer and the ceramic layer forms the capacitance unit of the capacitor.

[0048] Step S6: stacking the multiple ceramic sheets together and ensuring perfect overlap between the electrode layer and the ceramic layer.

[0049] Step S7: pressing the stacked layers using heat pressing or mechanical pressure.

[0050] Step S8: placing the laminated multi-layer sheet structure into a high-temperature sintering furnace for sintering.

[0051] Step S9, coating the terminal electrodes 4 at both ends of the sintered multilayer ceramic capacitor, usually using a three-layer structure of silver / nickel / tin to form a first anti-corrosion layer 401, a second anti-corrosion layer 402 and a third anti-corrosion layer 403; the perfect overlap and tight combination between the ceramic layer and the electrode layer ensures seamless electrical and mechanical contact between the layers, providing a basis for the high performance of the capacitor. This optimized lamination method effectively reduces the problem of unstable electrical performance caused by uneven or poor contact between layers, ensuring that the capacitor can operate stably under high frequency and high current conditions. Furthermore, the multilayer ceramic capacitor that has undergone high-temperature sintering treatment has greatly enhanced the bonding force between its layers, which not only improves the capacitor's ability to resist mechanical impact, but also extends its service life in high-temperature environments. During the sintering process, the density of the ceramic layer and the firm adhesion of the electrode layer are fully guaranteed, and the electrical performance of the capacitor remains stable after long-term use. At the same time, the terminal electrode 4 coated on the surface of the sintered multilayer chip ceramic capacitor includes a three-layer structure of tin, silver and nickel, which further enhances the connectivity of the capacitor with the external circuit. The corrosion-resistant design of the three-layer terminal electrode 4 effectively prevents metal migration and welding failure, thereby improving the adaptability of the capacitor in harsh environments and its reliability in long-term use.

[0052] The multilayer ceramic film and internal electrode layers are laminated to ensure perfect alignment between each ceramic layer and the internal electrode layer. The laminated structure is then sintered at a high temperature (typically 850°C–1000°C) to bond the ceramic layers to the internal electrode layers, forming the complete capacitor structure. The sintering process increases the density of the ceramic layers and strengthens the connection between the electrode layers. After sintering, terminal electrodes 4 are applied to the ends of the multilayer ceramic capacitor. Terminal electrodes 4 typically use a three-layer structure of silver / nickel / tin, forming the third anti-corrosion layer 403, the second anti-corrosion layer 402, and the first anti-corrosion layer 401. These electrodes are applied using electroplating techniques. This layer structure provides electrical connection between the capacitor and the external circuit and improves the capacitor's solderability. Finally, the capacitor undergoes surface treatment, such as plasma cleaning or laser trimming, to remove surface impurities and improve electrode contact quality. The capacitor is then packaged and ready for electrical performance testing, marking, and further packaging processes.

[0053] Step S10: packaging the capacitor.

[0054] Immerse the capacitor in the encapsulation material, or use compression molding to evenly coat the capacitor surface with the material. Compression molding ensures that the encapsulation material evenly covers the entire surface of the capacitor, especially the terminal electrodes. Heat curing: For materials such as epoxy resin, heat is used to cure them, ensuring that the encapsulation material is firmly attached to the capacitor surface. The curing process requires controlling the temperature and time to ensure that the encapsulation material cures evenly and achieves the best protection.

[0055] The particle size of the nickel particles in the internal electrode layer 3 is 10 nanometers to 500 nanometers.

[0056] Using nickel particles with a particle size range of 10 nanometers to 500 nanometers can effectively control the conductivity of the electrode while maintaining high antioxidant properties and good mechanical strength. The selection of this particle size range helps to improve the stability of the capacitor in high temperature and high humidity environments.

[0057] The second anti-corrosion layer 402 is an electroplating layer with a thickness of 0.1 μm to 2 μm.

[0058] Immerse the capacitor's terminal electrode 4 in a silver plating solution and electroplating a layer of silver onto the surface of the terminal electrode 4. Control the plating time and current density based on the capacitor's design requirements to ensure uniform deposition of the silver layer. Adjust the thickness of the silver layer by controlling the current density and plating time. The thickness is controlled between 0.1 μm and 2 μm to ensure good conductivity and solderability. During the plating process, ensure that the plating solution's temperature, stirring speed, and pH value are within the specified range to achieve a uniform silver layer.

[0059] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multilayer ceramic capacitor, characterized in that: include: A silicon base layer (1), a dielectric ceramic layer (2), an internal electrode layer (3) and an end electrode (4), wherein a pair of end electrodes (4) are provided above the silicon base layer (1), a plurality of internal electrode layers (3) are provided between the pair of end electrodes (4), and a dielectric ceramic layer (2) is provided between the plurality of internal electrode layers (3); The dielectric ceramic layer (2) comprises a nano-scale barium titanate plate, wherein the nano-scale barium titanate plate is doped with lanthanum oxide, strontium oxide, and calcium oxide; The internal electrode layer (3) is made of nickel particles and coated with rare earth oxide; The terminal electrode (4) includes: a first anti-corrosion layer (401), a second anti-corrosion layer (402) and a third anti-corrosion layer (403), the third anti-corrosion layer (403) is fixedly connected to the top of the silicon base layer (1), the second anti-corrosion layer (402) is provided on the top of the first anti-corrosion layer, and the third anti-corrosion layer (403) is provided on the top of the second anti-corrosion layer (402), the first anti-corrosion layer (401) is a tin layer, the second anti-corrosion layer (402) is a silver layer, and the third anti-corrosion layer (403) is a conductive layer composed of nickel particles, and the particle size of the nickel particles of the internal electrode layer (3) is 10 nanometers to 500 nanometers.

2. The multilayer ceramic capacitor according to claim 1, wherein: The second anti-corrosion layer (402) is an electroplating layer with a thickness of 0.1 μm to 2 μm.

3. A method for preparing a multilayer ceramic capacitor, characterized in that: For preparing a multilayer ceramic capacitor according to any one of claims 1 to 2, comprising: Step S1: mixing barium titanate plate powder with an appropriate amount of organic solvent, dispersant and binder, and performing ball milling or ultrasonic dispersion to ensure uniform dispersion of the powder and obtain a stable ceramic slurry; Step S2: Select appropriate nickel powder and mix it with a proper amount of binder and solvent to form an internal electrode slurry; Step S3, uniformly coating the prepared ceramic slurry on the carrier film by a tape casting method to form a film layer; Step S4: After drying, the film layer is cut into suitable sizes to obtain a plurality of dielectric ceramic sheets; Step S5: Print the prepared inner electrode slurry on the ceramic film, usually between alternating layers of the ceramic film, and print a layer of electrode on each layer of the ceramic film to form a multi-layer structure.

4. The method for preparing a multilayer ceramic capacitor according to claim 3, wherein: After step S5, the following steps are included: Step S6: stacking multiple layers of ceramic sheets together, and ensuring perfect overlap between the electrode layer and the ceramic layer; Step S7: pressing the stacked layers using heat pressing or mechanical pressure; Step S8, placing the laminated multilayer sheet structure into a high-temperature sintering furnace for sintering; Step S9: coating terminal electrodes (4) at both ends of the sintered multilayer ceramic capacitor, typically using a silver / nickel / tin three-layer structure, to form a first anti-corrosion layer (401), a second anti-corrosion layer (402), and a third anti-corrosion layer (403).

5. The method for preparing a multilayer ceramic capacitor according to claim 4, wherein: After S9, it also includes: Step S10: packaging the capacitor.

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