Ceramic silver electrode preparation method and ceramic capacitor

Abstract

The invention belongs to the technical field of ceramic capacitors, and discloses a preparation method of a ceramic silver electrode, which comprises the following steps: mixing a silver ammonia solution and a glucose solution, then spraying the mixture on a ceramic base surface, forming an upward arched cambered surface by the mixed solution under the action of surface tension, and forming a solution coacervation layer with the solution stacking amount decreasing gradually from the center to the periphery; in a protective gas atmosphere, heating for 10-30 minutes under the condition of 25-60 DEG C, so that a solution coacervate is primarily dried; the heating rate is controlled within the range of 1-2 DEG C / min in the heating process; then, the temperature is increased to 150-200 DEG C at the speed of 2-5 DEG C / min, heat preservation is conducted for 10-60 min, the preliminarily dried solution coacervate layer further reacts, and a densified silver layer is formed; and then, cooling to room temperature at the rate of less than or equal to 3 DEG C / min to obtain the silver electrode. Compared with a silk-screen printing or PVD (Physical Vapor Deposition) processing mode, the preparation method of the electrode is lower in cost, and the breakdown strength of the central area of the electrode is improved. The invention correspondingly discloses a ceramic capacitor which comprises the silver electrode prepared by the method.

Description

Technical Field

[0001] This invention belongs to the field of ceramic capacitor technology, specifically relating to a method for preparing a ceramic silver electrode and a ceramic capacitor. Background Technology

[0002] Ceramic capacitors are typically fabricated using methods such as printing or PVD sputtering. Printing or PVD sputtering methods have low printing efficiency, the paste is prone to overflowing from the electrode surface, PVD equipment is expensive, and the initial investment is large. Furthermore, the bonding strength between the electrode and the ceramic obtained by PVD sputtering requires a high degree of cleanliness and surface roughness of the ceramic surface.

[0003] Based on the research on the defects of existing products, the electrodes prepared by traditional printing or PVD sputtering are planar electrodes. However, the current-carrying position is the center point of the capacitor. Therefore, the common breakdown position of planar electrodes is the center point. If the breakdown strength of the electrode part needs to be improved, the thickness at the center point needs to be increased. However, the electrodes prepared by traditional printing or PVD sputtering are planar electrodes and cannot be made thicker at the center and thinner at the edges. If the overall thickness is increased, the material and processing costs will increase significantly.

[0004] To address the aforementioned issues, CN104319095A discloses a metallized thin film for capacitors and its manufacturing process. By vacuum evaporation, materials such as silver, aluminum, and zinc are deposited onto a base film to obtain a metallized thin film for capacitors comprising multiple coating units with varying thicknesses, thereby improving capacitor performance. However, this process is complex and not suitable for depositing metal materials onto ceramic substrates. Summary of the Invention

[0005] The purpose of this invention is to provide a simple and low-cost method for preparing ceramic silver electrodes and ceramic capacitors.

[0006] In a first aspect, the present invention provides a method for preparing a ceramic silver electrode, the technical solution of which is as follows: A method for preparing a ceramic silver electrode includes the following steps: Step 1: Mix silver ammonia solution and glucose solution and spray the mixture onto a ceramic substrate. Under the action of surface tension, the mixed solution forms an upward-arched surface and a solution condensation layer with the amount of solution stacking decreasing from the center to the periphery. Then, heat the mixture at 25-60℃ for 10-30 minutes in a protective gas atmosphere to allow the solution condensation layer to dry initially. During the heating process, control the heating rate within the range of 1-2℃ / min. Step 2: Increase the temperature to 150-200℃ at a rate of 2-5℃ / min and hold for 10-60min to allow the preliminarily dried solution condensation layer to react further and form a dense silver layer. Step 3: Cool to room temperature at a rate of ≤3℃ / min to obtain a silver electrode with a thickness that decreases from the center to the edge and has a smooth surface transition.

[0007] This invention, based on the aforementioned scheme, involves spraying a silver ammonia solution mixed with glucose to form a solution condensation layer that is thicker in the center and thinner at the edges, utilizing the surface tension of the liquid. By controlling the heating and cooling rates and temperatures during the initial drying and heat treatment steps, the initial drying removes most of the water, followed by heat treatment to form a dense silver layer. This allows the silver ammonia solution reaction in the solution condensation layer to create a silver electrode with a thickness that gradually decreases from the center to the edges. Because the electrode's energization is concentrated at the center point, by increasing the thickness of the silver layer in the central region (thinning at the edges), the center breakdown voltage is increased compared to printing or PVD processing methods, with the same amount of silver used.

[0008] Furthermore, in step one, a silver ammonia solution is sprayed onto the ceramic substrate using a nozzle; the nozzle includes several nozzles, the density of which decreases from the center to the periphery, forming several annular distribution zones. This type of nozzle facilitates the formation of a solution condensation layer with a decreasing solution accumulation from the center to the periphery.

[0009] Furthermore, the nozzle density in several annular distribution zones decreases from the inner circle to the outer circle.

[0010] Furthermore, the annular distribution zone is circular or polygonal in shape.

[0011] Furthermore, the diameter of the nozzle is in the range of 0.2-0.5mm, and the diameter of several nozzles is the same or decreases from the inner circle to the outer circle.

[0012] Furthermore, the nozzle includes an outer tube and an inner tube arranged coaxially; wherein, one end of the outer tube is connected to a first liquid inlet pipe, and the other end is connected to an atomizing head, and the spray hole is opened in the atomizing head; both ends of the inner tube are fixedly connected to the inner wall of the outer tube, forming a liquid supply chamber between them, and a second liquid inlet pipe connected to the liquid supply chamber is connected to the outer tube; the inner cavity of the inner tube includes a first diameter-changing section, a uniform diameter section and a second diameter-changing section connected in sequence, and the diameters of the first diameter-changing section and the second diameter-changing section gradually decrease towards the uniform diameter section; a connecting hole connecting the uniform diameter section and the liquid supply chamber is opened in the inner tube wall, and the axis of the connecting hole is perpendicular to the axis of the inner tube.

[0013] By adopting the above technical solution, glucose solution and silver ammonia solution can be introduced into the inner tube through the first inlet pipe and the second inlet pipe respectively. After the two are mixed evenly in the inner tube, they are quickly sprayed out from the atomizing head. After subsequent heat treatment, they can react to form a silver electrode.

[0014] Furthermore, both the outer and inner tubes are made of polytetrafluoroethylene (PTFE), and the first inlet tube and the atomizing head are detachably connected to the outer tube. When silver ammonia solution and glucose solution are mixed, some elemental silver particles will inevitably be generated. The low surface energy of PTFE can reduce the adhesion of elemental silver to the tube wall to some extent, reducing clogging problems. On the other hand, the detachable connection between the first inlet tube and the atomizing head facilitates replacement or cleaning.

[0015] Furthermore, in step one, the concentration of the silver ammonia solution is 5-10% (w / v), and the concentration of the glucose solution is 10-20% (w / v), with a volume ratio of 1:(1-2). Silver ammonia solutions within this concentration range are easy to spray evenly and have good adhesion to the substrate.

[0016] Furthermore, after completing step one, repeat step one twice before proceeding to step two; in step one, control the maximum thickness of the solution coagulation layer after each spraying to be 1-2 μm, which is more conducive to electrodes with good integrity and conductivity.

[0017] Furthermore, the concentration of the silver ammonia solution used in the first spraying is 5-6.5% (w / v), the concentration in the second spraying is 6.5-8.5% (w / v), and the concentration in the third spraying is 8.5-10% (w / v). Compared to electrodes produced by a single spraying, this method results in better electrode density, superior conductivity, and reduces the likelihood of cracking or blistering during manufacturing.

[0018] Furthermore, in step one, the initial drying temperature is 40-60℃.

[0019] Furthermore, in step one, before spraying the silver ammonia solution, the ceramic substrate is cleaned and / or roughened to improve the adhesion of the silver electrode to the ceramic substrate.

[0020] Furthermore, the ceramic substrate surface is roughened by mechanical grinding, sandblasting, chemical etching, laser processing, or plasma treatment.

[0021] Secondly, the present invention provides a ceramic capacitor, the technical solution of which is as follows: A ceramic capacitor includes a silver electrode, which is prepared by any of the preceding methods for preparing a ceramic silver electrode.

[0022] The present invention has the following beneficial effects: 1. Silver is initially sprayed onto the ceramic surface in the form of a silver ammonia solution. Compared with traditional printing or PVD sputtering methods, the penetration and fusion with the ceramic surface are greatly improved. The method for preparing the silver electrode of the ceramic capacitor of the present invention reduces the requirements for the cleanliness and roughness of the substrate. 2. The amount of silver ammonia solution stacked in the center region of the electrode is higher than that in the edge region, and the overall upper surface is arc-shaped under the action of surface tension. After solidification, a silver electrode with a thick center and a thickness decreasing towards the edge is formed. The breakdown strength of the electrode center region is improved without increasing the overall thickness of the silver electrode, thus reducing production costs. 3. In the preferred embodiment, multiple spraying processes can be used to obtain electrodes with higher density. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the ceramic silver electrode preparation method in Example 1; Figure 2 This is a schematic diagram of the nozzle structure in the embodiment; Figure 3 This is a cross-sectional view of the nozzle in the embodiment; Figure 4 This is a schematic diagram of the atomizing head in the embodiment; Figure 5 This is a diagram illustrating the process of preparing the ceramic silver electrode in Example 1. Figure 6 This is a process flow diagram of the ceramic silver electrode preparation method in Example 5; Figure 7 This is a diagram illustrating the process of preparing the ceramic silver electrode in Example 5. Figure 8 This is a process flow diagram of the ceramic silver electrode preparation method in Example 6.

[0024] Explanation of reference numerals in the attached figures: 1. Nozzle; 11. Outer tube; 111. First inlet pipe; 112. Second inlet pipe; 113. Liquid supply chamber; 12. Inner tube; 121. First diameter changing section; 122. Uniform diameter section; 123. Second diameter changing section; 124. Connecting hole; 13. Atomizing head; 131. Spray hole; 2. Ceramic substrate; 3. Solution condensation layer. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions of this invention, the present application will be further described in detail below with reference to the accompanying drawings.

[0026] This invention provides a method for preparing a ceramic silver electrode, comprising the following steps: The silver ammonia solution preparation process is as follows: First, dissolve silver nitrate in deionized water, then add ammonia water dropwise while stirring until the brown precipitate is completely dissolved and the solution becomes clear. Finally, dilute with deionized water to the required concentration. This invention uses a spray coating method to apply the solution, requiring consideration of both spraying operability and the conductivity of the resulting silver electrode. Therefore, the concentration of the silver ammonia solution is best controlled at 5-10% (w / v). Too low a concentration is detrimental to obtaining a dense electrode with excellent conductivity, while too high a concentration may result in uneven spraying, ultimately leading to defects such as poor adhesion to the substrate.

[0027] Glucose solution preparation process: Dissolve glucose in deionized water, disperse evenly, and then dilute with deionized water to the required concentration. The glucose solution prepared in this invention has a concentration of 10-20% (w / v).

[0028] Ceramic substrate cleaning process: Place the piezoelectric ceramic substrate in an alkaline cleaning solution of 40g / L sodium hydroxide, 50g / L sodium carbonate, and 30g / L sodium phosphate, immerse at 80℃ for 30 minutes, remove, clean, and dry.

[0029] Solution mixing and spraying process: The prepared silver ammonia solution and glucose solution are mixed evenly using a spray nozzle and then sprayed onto a cleaned ceramic substrate. Under surface tension, the mixed solution forms an upward-arched surface, creating a solution coagulation layer with decreasing solution accumulation from the center to the periphery. The mixing ratio of silver ammonia solution and glucose solution is generally 1:(1-2) by volume, and the spraying distance should be controlled at 10-20cm. Specific adjustments can be made based on the solubility of the prepared solution to ensure sufficient reaction of the silver ammonia solution in subsequent processes to form a silver layer.

[0030] Preliminary drying process: The ceramic substrate after spraying the mixed solution is heated in a protective gas atmosphere at 25-60℃ for 10-30 minutes to allow most of the moisture in the solution condensation layer to evaporate and achieve preliminary drying. It should be noted that the heating rate during this step should not be too fast and should be controlled within the range of 1-2℃ / min. Otherwise, it may easily disrupt the state of the solution condensation layer with decreasing solution accumulation from the center to the periphery, which is not conducive to the formation of a continuous and well-adhesive silver layer.

[0031] Heat treatment process: After initial drying, the temperature is raised to 150-200℃ at a rate of 2-5℃ / min and held for 10-60min to allow the solution coagulation layer to react further and form a dense silver layer; in order to obtain a motor with good conductivity and reduce the cracking and blistering temperature during the preparation process, the heat treatment process also needs to strictly control the heating rate.

[0032] And the cooling process: cooling to room temperature at a rate of ≤3℃ / min to obtain a silver electrode with a thickness that decreases from the center to the edge and a smooth surface transition.

[0033] In different embodiments, a silver layer of the required thickness can be prepared by spraying once or multiple times. For example, after repeating the "spraying-preliminary drying" operation several times, a uniform heat treatment is performed to form a silver layer; or, the "spraying-preliminary drying-heat treatment" steps are repeated multiple times to form a silver layer of the desired thickness.

[0034] The present invention provides a ceramic capacitor comprising a silver electrode prepared by the aforementioned method.

[0035] [Example 1] A method for preparing a ceramic silver electrode, referring to Figure 1 and Figure 5 This embodiment uses a single-coating process, and the specific steps are as follows: S1 Solution Spraying: A 5% (w / v) silver ammonia solution and a 20% (w / v) glucose solution are mixed at a volume ratio of 1:1 and sprayed onto a cleaned ceramic substrate 2. Under the action of surface tension, the mixed solution forms an upward-arched arc surface, creating... Figure 5 The solution condensation layer 3 is shown as having a decreasing amount of solution stacking from the center to the periphery.

[0036] Solution spraying is accomplished through nozzle 1, which has a solution mixing function, as shown in the reference. Figure 2 and Figure 3 The nozzle 1 includes an outer tube 11 and an inner tube 12 coaxially arranged. The diameter of the inner tube 12 is smaller than the inner diameter of the outer tube 11, forming a gap between them. The end of the inner tube 12 extends and is fixed to the inner wall of the outer tube 11, thereby forming a closed liquid supply chamber 113 between the outer tube 11 and the inner tube 12. One end of the outer tube 11 is threadedly connected to a first liquid inlet pipe 111, which communicates with the inner tube 12 to supply glucose solution. Conventional devices necessary for solution supply, such as dispensing devices, pipelines, and metering pumps, are not shown in the figure. Achieving quantitative supply of liquids such as glucose solution using known means such as metering pumps is a well-known technical method in the art and will not be described in detail here.

[0037] Reference Figure 1 and Figure 2 The inner cavity of the inner tube 12 includes a first variable diameter section 121, a uniform diameter section 122, and a second variable diameter section 123 connected in sequence. The inner diameters of both the first variable diameter section 121 and the second variable diameter section 123 gradually decrease towards the uniform diameter section 122, forming a funnel shape. Thus, the glucose solution supplied by the first inlet pipe 111 exhibits a flow rate that first increases and then decreases as it flows through the first variable diameter section 121, the uniform diameter section 122, and the second variable diameter section 123 in sequence.

[0038] Reference Figure 1 and Figure 3A second inlet pipe 112 is connected to the outer tube 11 along the vertical axis to supply silver ammonia solution to the supply chamber 113. Similar to the supply of glucose solution, the silver ammonia solution can be supplied using known metering pumps, which will not be elaborated here. A connecting hole 124 is opened on the inner tube 12 along the vertical axis, connecting the uniform diameter section 122 of the inner tube 12 to the supply chamber 113. The glucose solution flowing through the uniform diameter section 122 has a higher flow rate, allowing the silver ammonia solution in the supply chamber 113 to be introduced into the uniform diameter section 122 through the connecting hole 124, mixed evenly, and then discharged through the second variable diameter section 123. In this way, the silver ammonia solution and glucose solution can be quickly and evenly mixed before being sprayed out, minimizing nozzle clogging due to the short residence time. Meanwhile, in this embodiment, the inner tube 12, outer tube 11, first liquid inlet tube 111 and second liquid inlet tube 112 of the nozzle 1 are all made of polytetrafluoroethylene material, so the generated silver particles are not easy to adhere to the inner wall.

[0039] Reference Figure 2 , Figure 3 and Figure 5 The other end of the outer tube 11 is threadedly connected to an atomizing head 13 made of polytetrafluoroethylene. The atomizing head 13 has several spray holes 131 on its end face, which are used to atomize the mixed solution discharged through the second reducing section 123 and spray it onto the ceramic substrate 2. The first liquid inlet tube 111 and the atomizing head 13 are both threadedly connected to the outer tube 11, and can be disassembled and replaced or cleaned if necessary.

[0040] Reference Figure 4 and Figure 5 To form a solution condensation layer 3 where the amount of solution stacking decreases from the center to the periphery, the distribution density of the nozzles 131 on the atomizing head 13 decreases from the center to the periphery, forming several annular distribution bands. In other embodiments, depending on the shape of the electrode to be processed, the annular distribution bands of the nozzles 131 can be rectangular or other shapes. The density of the nozzles 131 in the several annular distribution bands decreases continuously or stepwise from the inner circle to the outer circle. The diameter of the nozzles 131 is all in the range of 0.2-0.5 mm, and the diameter of several of the nozzles 131 is the same or decreases from the inner circle to the outer circle. In this embodiment, there are a total of five nozzle diameters on the atomizing head 131, with the nozzle diameters from the inner circle to the outer circle being 0.5 mm, 0.45 mm, 0.4 mm, 0.3 mm, and 0.2 mm respectively.

[0041] S2 Preliminary Drying: Under a protective gas atmosphere, the temperature is increased to 60°C at a rate of 2°C / min and heated for 10 minutes to allow the solution condensation layer to dry initially.

[0042] S3 heat treatment: Heat to 150℃ at a rate of 2℃ / min and hold for 60min to allow the initially dried solution condensation layer to react further and form a dense silver layer.

[0043] S4 Cooling: Cool to room temperature at a rate of 1.5℃ / min to obtain a silver electrode with a thickness decreasing from the center to the edge and a smooth surface transition.

[0044] [Examples 2-4] Examples 2-4 are all based on Example 1, with the only difference being the different process parameters for each step.

[0045] Table 1. Process parameters for Examples 1-4

[0046] Silver electrodes were obtained in Examples 2-4.

[0047] [Example 5] A method for preparing a ceramic silver electrode, Example 5 is based on Example 1, the difference being that: this example adopts a "multiple spraying followed by unified heat treatment" process, that is, first complete the "solution spraying-preliminary drying" operation once, then repeat the operation twice, and then perform heat treatment to obtain a silver electrode of the expected thickness.

[0048] Reference Figure 6 and Figure 7 The specific steps are as follows: S1 Single Spray: Mix 5-6.5% (w / v) silver ammonia solution and 20% (w / v) glucose solution at a volume ratio of 1:1 and spray the mixture onto the ceramic substrate 2. Under the action of surface tension, the mixed solution forms an upward-arched arc surface, forming... Figure 7 The solution condensation layer 3 is shown as having a decreasing solution stacking amount from the center to the periphery. In this embodiment, the concentration of the silver ammonia solution sprayed in one application is 6% (w / v), and the maximum thickness of the solution condensation layer after spraying is 1-2 μm.

[0049] S2 First drying: In a protective gas atmosphere, the temperature is increased to 60°C at a rate of 2°C / min and heated for 10 minutes to allow the solution condensate layer to dry initially. S2 Secondary Spraying: A 6.5-8.5% (w / v) silver ammonia solution and a 20% (w / v) glucose solution are mixed at a volume ratio of 1:1 and sprayed onto the ceramic substrate 2. Under the action of surface tension, the mixed solution forms an upward-arched arc surface, forming... Figure 5 The solution condensation layer 3 is shown as having a decreasing amount of solution stacking from the center to the periphery. In this embodiment, the concentration of the silver ammonia solution used in the secondary spraying is 7.5% (w / v), and the maximum thickness of the solution condensation layer after spraying is 1-2 μm.

[0050] S4 Secondary Drying: Under a protective gas atmosphere, the temperature is increased to 60°C at a rate of 2°C / min and heated for 10 minutes to allow the solution condensate layer to dry initially. S5 Triple Coating: An 8.5-10% (w / v) silver ammonia solution and a 20% (w / v) glucose solution are mixed at a volume ratio of 1:1 and sprayed onto the ceramic substrate 2. Under surface tension, the mixed solution forms an upward-arched arc surface, creating... Figure 5 The solution condensation layer 3 is shown as having a decreasing solution stacking amount from the center to the periphery. In this embodiment, the concentration of the silver ammonia solution sprayed three times is 9% (w / v), and the maximum thickness of the solution condensation layer after spraying is 1-2 μm.

[0051] S5 three-stage drying: In a protective gas atmosphere, the temperature is increased to 60°C at a rate of 2°C / min and heated for 10 minutes to allow the solution condensate layer to dry initially. S6 heat treatment: Heat to 150℃ at a rate of 2℃ / min and hold for 60min to allow the initially dried solution condensation layer to react further and form a dense silver layer. S7 Cooling: Cool to room temperature at a rate of 1.5℃ / min to obtain a silver electrode with a smooth transition of thickness from the center to the edge.

[0052] [Example 6] A method for preparing a ceramic silver electrode, Example 6, is based on Example 5, with the difference that: heat treatment is performed after each "solution spraying-preliminary drying" process, and the "solution spraying-preliminary drying-heat treatment" operation is repeated three times to obtain a silver electrode of the desired thickness. The three-stage heat treatment allows for gradual densification of the silver layer, reduces interfacial porosity, and lowers dielectric loss compared to a single-step process. (Refer to...) Figure 8 The specific steps are as follows: Reference Figure 6 The specific steps are as follows: S1 Single Spray: A 6% (w / v) silver ammonia solution and a 20% (w / v) glucose solution are mixed at a volume ratio of 1:1 and sprayed onto the ceramic substrate 2. Under the action of surface tension, the mixed solution forms an upward-arched arc surface, forming... Figure 7 The solution condensation layer 3 is shown as having a decreasing amount of solution stacking from the center to the periphery.

[0053] S2 First drying: In a protective gas atmosphere, the temperature is increased to 60°C at a rate of 2°C / min and heated for 10 minutes to allow the solution condensate layer to dry initially. S3 First heat treatment: Heat to 150℃ at a rate of 2℃ / min and hold for 60min to allow the pre-dried solution condensation layer to react further and form a dense inner silver layer. S4 Secondary Spraying: A 7.5% (w / v) silver ammonia solution and a 20% (w / v) glucose solution are mixed at a volume ratio of 1:1 and sprayed onto the ceramic substrate 2. Under the action of surface tension, the mixed solution forms an upward-arched arc surface, forming... Figure 5The solution condensation layer 3 is shown as having a decreasing amount of solution stacking from the center to the periphery.

[0054] S5 Secondary Drying: Under a protective gas atmosphere, the temperature is increased to 60°C at a rate of 2°C / min and heated for 10 minutes to allow the solution condensate layer to dry initially. S6 Secondary heat treatment: Heat to 150℃ at a rate of 2℃ / min and hold for 60min to allow the initially dried solution condensation layer to react further and form a dense intermediate silver layer. S7 Triple Coating: A 9% (w / v) silver ammonia solution and a 20% (w / v) glucose solution are mixed at a volume ratio of 1:1 and sprayed onto the ceramic substrate 2. Under the action of surface tension, the mixed solution forms an upward-arched arc surface, forming... Figure 5 The solution condensation layer 3 is shown as having a decreasing amount of solution stacking from the center to the periphery.

[0055] S8 three-stage drying: In a protective gas atmosphere, the temperature is increased to 60°C at a rate of 2°C / min and heated for 10 minutes to allow the solution condensate layer to dry initially. S9 undergoes three heat treatments: the temperature is increased to 150℃ at a rate of 2℃ / min and held for 60min to allow the initially dried solution condensation layer to react further and form a dense outer silver layer. S7 Cooling: Cooling to room temperature at a rate of 1.5℃ / min to obtain a silver electrode with a smooth transition surface and a thickness that decreases from the center to the edge. The silver electrode consists of an inner silver layer, a middle silver layer, and an outer silver layer stacked together.

[0056] [Application Examples 1-6] A ceramic capacitor, wherein the terminal electrodes are prepared using the methods of Examples 1-6 respectively.

[0057] [Performance Testing] Visual inspection: The surface morphology is observed under a microscope to check for pores, cracks, etc., to indirectly assess conductivity. Electrodes with uniform and defect-free surfaces generally have better conductivity. The results are recorded in Table 2.

[0058] Adhesion test: Ceramic capacitors prepared according to the methods in Application Examples 1-6 were randomly selected, and the adhesion of the terminal electrodes was tested. The test method in GB / T 9286-2021 was referred to, and the average value of multiple test results was recorded in Table 2.

[0059] Dielectric loss: Ceramic capacitors prepared according to the methods in Application Examples 1-6 were randomly selected and their dielectric loss was tested. Using a Tonghui TH2838 precision LCR digital bridge instrument, the capacitance and loss of the prepared ceramic capacitor disc with a diameter of 14 mm and a thickness of 4 mm were tested at 1 kHz and room temperature. The average value of multiple test results was recorded in Table 2.

[0060] Breakdown voltage: Ceramic capacitor discs with a diameter of 14 mm and a thickness of 4 mm prepared according to the methods in Application Examples 1-6 were randomly selected. Using the Yangzi YD10013 ultra-high voltage tester, the ceramic discs were immersed in silicone oil and their breakdown resistance was tested at room temperature. The average value of multiple test results was recorded in Table 2.

[0061] Table 2. Performance Test Results

[0062] The data in the table above shows that the method of this invention can prepare silver electrodes with no obvious appearance defects, a thickness that decreases from the center to the edge, and a smooth surface transition. These electrodes are thicker in the middle region, resulting in better breakdown resistance. In the application examples, the dielectric loss and end electrode adhesion of the resulting ceramic capacitors are equal to or better than those prepared using conventional methods with silver electrodes. Furthermore, experimental data shows that using a multi-stage spraying method to prepare the electrodes is more conducive to improving adhesion and reducing dielectric loss.

[0063] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for preparing a ceramic silver electrode, characterized in that, Includes the following steps: Step 1: Mix silver ammonia solution and glucose solution and spray them onto the ceramic substrate (2). Under the action of surface tension, the mixed solution forms an arched surface and a solution condensation layer (3) with the amount of solution stacking decreasing from the center to the periphery. Then, in a protective gas atmosphere, heat at 25-60℃ for 10-30 min to allow the solution condensation layer (3) to dry initially. During the heating process, control the heating rate in the range of 1-2℃ / min. Step 2: Increase the temperature to 150-200℃ at a rate of 2-5℃ / min and hold for 10-60min to allow the pre-dried solution condensation layer (3) to react further and form a dense silver layer. Step 3: Cool to room temperature at a rate of ≤3℃ / min to obtain a silver electrode with a thickness that decreases from the center to the edge and has a smooth surface transition.

2. The method for preparing a ceramic silver electrode according to claim 1, characterized in that: In step one, the silver ammonia solution and glucose solution are mixed and sprayed onto the ceramic substrate (2) using a nozzle (1); the nozzle (1) includes several nozzles (131), and the distribution density of the nozzles (131) decreases from the center to the periphery, forming several annular distribution zones.

3. The method for preparing a ceramic silver electrode according to claim 2, characterized in that: The density of nozzles (131) in several annular distribution zones decreases from the inner circle to the outer circle.

4. The method for preparing a ceramic silver electrode according to claim 2, characterized in that: The annular distribution zone is circular or a regular polygonal ring.

5. The method for preparing a ceramic silver electrode according to any one of claims 2-4, characterized in that: The diameter of the nozzle (131) is in the range of 0.2-0.5 mm, and the diameter of several nozzles (131) is the same or decreases from the inner circle to the outer circle.

6. The method for preparing a ceramic silver electrode according to claim 1, characterized in that: In step one, the concentration of silver ammonia solution is 5-10% (w / v) and the concentration of glucose solution is 10-20% (w / v), and the volume ratio of the two is 1:(1-2).

7. The method for preparing a ceramic silver electrode according to claim 6, characterized in that: After completing step one, repeat step one twice, and then proceed to step two; in step one, control the maximum thickness of the solution coagulation layer (3) after each spraying to be 1-2 μm.

8. The method for preparing a ceramic silver electrode according to claim 7, characterized in that: The concentration of the silver ammonia solution for the first spray is 5-6.5% (w / v), the concentration for the second spray is 6.5-8.5% (w / v), and the concentration for the third spray is 8.5-10% (w / v).

9. The method for preparing a ceramic silver electrode according to claim 1, characterized in that: In step one, the initial drying temperature is 40-60℃.

10. A ceramic capacitor comprising silver electrodes, characterized in that, The silver electrode is prepared by the method for preparing a ceramic silver electrode according to any one of claims 1-9.

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