A method for preparing a silver electrode

Abstract

The application discloses a preparation method of a silver electrode and belongs to the technical field of metalization of electronic components. The method comprises four steps of glass raw material preparation, glass powder preparation, silver paste preparation and silver electrode sintering, adopts modified nickel powder, tungsten powder and other conductive additives to replace part of silver, matches SiO2-B2O3-Bi2O3-Na2CO3-Al2O3 glass powder, and controls the mass percentage of silver powder to be 12-72 wt.%. The application solves the defects of high silver content, high cost or poor conductive performance in the prior art, the prepared silver electrode has a compact structure and stable conductivity, the process is simple, the silver electrode can be industrially produced, and the production cost of electronic components is effectively reduced.

Description

Technical Field

[0001] This invention belongs to the field of electronic component metallization technology, specifically a method for preparing a silver electrode. Background Technology

[0002] With the accelerated development of the global artificial intelligence industry, the price increase trend in the semiconductor field has spread from memory chips to various electronic components. Among them, the market prosperity of ceramic electronic components such as MLCCs (multilayer ceramic capacitors), known as the "rice of the electronics industry," continues to rise, driving a significant increase in the demand for silver electrodes. As a core component of ceramic packaging substrates and ceramic electronic components, the performance of silver electrodes directly determines the stability and lifespan of electronic components. Currently, silver electrodes on the market are mainly composed of silver, glass, and ceramics, with a silver content typically exceeding 50 wt.%. As a core conductive component, the amount of silver used directly affects the conductivity of the electrode. In recent years, the market price of silver has continued to rise sharply, leading to a dramatic increase in the production cost of electronic components. Leading domestic electronic component companies have raised the prices of silver electrode-related products, with price increases of 10% to 20% for products such as varistors and ceramic capacitors. Major Japanese MLCC manufacturers such as Murata and TDK are also planning to raise prices for related products, with increases potentially reaching 20%. This has severely squeezed the profit margins of the electronic component manufacturing industry. Therefore, designing electrodes with lower silver content to reduce production costs while ensuring the core performance of the electrodes is of great practical significance for the sustainable development of the electronic component manufacturing industry.

[0003] In existing technologies, there are two main approaches to reducing the cost of silver electrodes: one is to increase the content of glass powder, replacing some of the silver inside the electrode with glass; the other is to directly replace silver with other inexpensive metal powders. However, both approaches have significant drawbacks. Increasing the glass powder content significantly reduces the conductivity of the silver electrode due to the poor conductivity of glass, leading to increased sheet resistance and affecting the signal transmission efficiency of electronic components. Furthermore, this method can only reduce the silver content to a minimum of about 50 wt.%, which is insufficient to meet the need for further cost reduction. Replacing silver with unmodified inexpensive metal powder results in poor compatibility between the metal powder and silver or glass powder, leading to numerous pores inside the electrode, insufficient structural density, and susceptibility to problems such as detachment and oxidation, severely impacting the electrode's lifespan and reliability. Furthermore, as electronic components develop towards miniaturization and high frequency, higher requirements are placed on the density and conductivity stability of silver electrodes. Existing technologies are unable to meet the dual demands of low cost and high performance. Therefore, developing a preparation method that can significantly reduce the silver content while ensuring the conductivity and structural density of silver electrodes has become an urgent technical problem to be solved in this field. Summary of the Invention

[0004] To address the shortcomings of existing technologies, such as high silver content and high cost of silver electrodes, and the decrease in conductivity caused by reducing silver content through increasing glass powder content, this invention provides a method for preparing silver electrodes. By replacing part of the silver with modified conductive additives and combining them with glass powder that has excellent sintering properties, the silver content is significantly reduced while ensuring the conductivity and structural density of the silver electrode, thereby effectively reducing production costs.

[0005] To achieve the above objectives, the present invention employs the following technical means:

[0006] A method for preparing a silver electrode includes the following steps:

[0007] 1) Preparation of glass raw materials: Weigh each raw material according to the mass ratio, and ball mill them together for 24 hours with ethanol as solvent at a ratio of glass:ethanol:zirconium balls = 1:1:4; after pressing and filtering the uniformly mixed raw materials, dry them at 100℃ for 24 hours, and pass them through a 100-mesh sieve to obtain raw material powder; melt the raw material powder at a high temperature of 1400-1600℃ for 0.5-2 hours, and quench the glass melt in distilled water to obtain glass slag;

[0008] 2) Preparation of glass powder: Take the glass slag prepared in step 1) and crush it by planetary ball milling with ethanol as solvent at a ratio of glass slag: ethanol: zirconium balls = 1:1:4; suspend the crushed glass powder in ethanol and pressurize it by hydraulic filtration, dry it at 100℃ for 24h, and pass it through a 200-mesh sieve to obtain glass powder with an average particle size of 0.5~3.0μm.

[0009] 3) Preparation of silver paste: Weigh each raw material according to the mass percentage. The raw materials include 10-60 wt.% silver powder, 3-20 wt.% glass powder prepared in step 2), 3-40 wt.% conductive additives, and 15-30 wt.% organic carrier. Mix the weighed raw materials in a high-speed mixer at a speed of 800-2000 rpm for 10-20 minutes. Then, roll the uniformly mixed paste with three rollers to obtain a uniform silver paste.

[0010] 4) Sintering of silver electrodes: Take the silver paste prepared in step 3) and form electrodes on the surface of the component by screen printing or silver dipping process. Then, heat the electrode to 500-750℃ at a heating rate of 1-10℃ / min and sinter for 1-60min. After cooling, the silver electrode is obtained. The internal elements of the silver electrode are analyzed and found to contain silver, glass and conductive additives.

[0011] Preferably, in step 1), the glass raw material is made of SiO2, B2O3, Bi2O3, Na2CO3, and Al2O3.

[0012] Preferably, in step 1), the diameter of the zirconium ball is 5 mm.

[0013] Preferably, in step 2), the zirconium balls are divided into three sizes: large, medium, and small, with diameters of 15mm, 10mm, and 5mm respectively, and the ratio of large ball: medium ball: small ball = 1:1:3.

[0014] Preferably, in step 3), the silver powder is spherical with a diameter in the range of 0.05 to 2.5 μm.

[0015] Preferably, in step 3), the conductive additive is one or more of the following: surface-modified nickel powder, tungsten powder, molybdenum powder, and copper powder.

[0016] Preferably, in step 3), the organic carrier is a mixture of terpineol and ethyl cellulose.

[0017] Preferably, in step 3), the rolling process parameters are: rotation speed 100-150 rpm, step size 10-20 μm, maximum gap 80-100 μm, minimum gap 5-15 μm, and gap difference between the two rollers 10-20 μm.

[0018] Preferably, in step 4), the silver electrode contains silver, glass, and conductive additives, wherein the electrode contains 12–72 wt.% silver powder, 4–24 wt.% glass powder prepared in step 2), and 4–48 wt.% conductive additives.

[0019] The present invention has the following beneficial effects:

[0020] 1. Good electrode density: Combined with SiO2, B2O3, Bi2O3, Na2CO3 and Al2O3 glass powders with excellent sintering properties, and with optimized preparation process, the prepared silver electrode has a dense structure, smooth surface without obvious protrusions and depressions, and high bonding strength with ceramic substrate, which meets the actual application requirements of electronic components.

[0021] 2. Significantly reduce silver content and production costs: This invention replaces part of the silver with modified nickel powder, tungsten powder, molybdenum powder, and copper powder conductive additives, which can reduce the silver content in the silver electrode to as low as about 12 wt.%, compared with the minimum silver content of 50 wt.% in the prior art. The amount of silver used is greatly reduced, which effectively reduces the cost pressure caused by the rise in silver prices.

[0022] 3. Ensure electrode conductivity: The conductive additives used have good conductivity and, after modification, have excellent compatibility with silver powder and glass powder. This avoids the problem of a significant decrease in conductivity caused by adding a large amount of glass in existing technologies, ensuring that the silver electrode has stable conductivity.

[0023] 4. Simple process and strong operability: The preparation process of this invention is clear, and the process parameters of each step are well-defined. It does not require complex equipment or special operating conditions, which facilitates large-scale industrial production.

[0024] 5. Ensure electrode conductivity: The conductive additives used have good conductivity and, after modification, have excellent compatibility with silver powder and glass powder. This avoids the problem of a significant decrease in conductivity caused by adding a large amount of glass in existing technologies, ensuring that the silver electrode has stable conductivity. Attached Figure Description

[0025] Figure 1 This is a microstructure diagram of the surface of the silver electrode of the present invention (the mass ratio of Ni:Ag:glass is 25:28:19).

[0026] Figure 2 This is a microstructure diagram of the cross-section of the silver electrode of the present invention (the mass ratio of Ni:Ag:glass is 25:28:19).

[0027] Figure 3 The images show the microstructure of the silver electrode on the surface of the component in Embodiment 1 of the present invention, where (a) is a 3000x magnified image and (b) is a 300x magnified image.

[0028] Figure 4 The images shown are microstructure diagrams of the silver electrode on the surface of the component in Comparative Example 1 of the present invention, where (a) is a 3000x magnified view and (b) is a 300x magnified view.

[0029] Figure 5 The images show the microstructure of the silver electrode on the surface of the component in Embodiment 2 of the present invention, where (a) is a 3000x magnified image and (b) is a 300x magnified image.

[0030] Figure 6 The images shown are microstructure diagrams of the silver electrode on the surface of the component in Embodiment 3 of the present invention, where (a) is a 3000x magnified image and (b) is a 300x magnified image. Detailed Implementation

[0031] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] A method for preparing a silver electrode includes the following steps:

[0033] 1. Preparation of glass raw materials: Weigh each raw material according to the mass ratio, and ball mill them together for 24 hours with ethanol as solvent at a ratio of glass:ethanol:zirconium balls = 1:1:4, wherein the diameter of the zirconium balls is 5 mm; after pressing and filtering the uniformly mixed raw materials, dry them at 100℃ for 24 hours, and pass them through a 100-mesh sieve to obtain raw material powder; melt the raw material powder at a high temperature of 1400-1600℃ for 0.5-2 hours, and quench the glass melt in distilled water to obtain glass slag.

[0034] 2. Preparation of glass powder: The glass slag prepared in step 1 was crushed by planetary ball milling with ethanol as solvent at a ratio of glass slag:ethanol:zirconium balls = 1:1:4. The zirconium balls were divided into three sizes: large, medium, and small, with diameters of 15 mm, 10 mm, and 5 mm, respectively, and the ratio of large balls:medium balls:small balls = 1:1:3. The crushed glass powder was suspended in ethanol and filtered by hydraulic pressure, dried at 100℃ for 24 h, and passed through a 200-mesh sieve to obtain SiO2, B2O3, Bi2O3, Na2CO3, and Al2O3 glass powder with an average particle size (D50) of 0.5–3.0 μm. This glass powder has excellent bonding strength with silver powder and high bonding strength with ceramics.

[0035] 3. Preparation of silver paste: Weigh each raw material according to the mass percentage. The raw materials include 10-60 wt.% silver powder, 3-20 wt.% glass powder prepared in step 2, 3-40 wt.% conductive additive, and 15-30 wt.% organic carrier. The silver powder is spherical with a diameter in the range of 0.05-2.5 μm. The conductive additive is one or more of surface-modified nickel powder, tungsten powder, molybdenum powder, and copper powder. The organic carrier is a mixture of terpineol and ethyl cellulose. Mix the weighed raw materials in a high-speed mixer at a speed of 800-2000 rpm for 10-20 min. Then, roll the uniformly mixed paste into a three-roll mill. The rolling process parameters are: speed 100-150 rpm, step 10-20 μm, maximum gap 80-100 μm, minimum gap 5-15 μm, and gap difference between the two rollers 10-20 μm to obtain a uniform silver paste.

[0036] 4. Sintering of silver electrodes: Take the silver paste prepared in step 3 and form electrodes on the surface of the component by screen printing or silver dipping process. Then, heat the electrode to 500-750℃ at a heating rate of 1-10℃ / min and sinter for 1-60min. After cooling, the silver electrode is obtained. The internal elements of the silver electrode are analyzed and found to contain silver, glass and conductive additives.

[0037] Furthermore, the mass percentages of the components in the prepared silver electrode are: 12–72 wt.% silver powder, 4–24 wt.% glass powder prepared in step 2, and 4–48 wt.% conductive additives. When the mass ratio of Ni:Ag:glass in the silver electrode is 25:28:19, its microstructure is as follows. Figure 1 , Figure 2 As shown, Figure 1 This shows the surface microstructure of the silver electrode at this ratio. Figure 2 Its cross-sectional microstructure can intuitively demonstrate the structural characteristics of the silver electrode prepared by this invention under a reasonable component ratio.

[0038] Furthermore, the conductive additive undergoes surface modification treatment. The modified conductive additive exhibits good compatibility with silver powder and glass powder, preventing pores within the electrode, ensuring the electrode's density and conductivity, and avoiding oxidation during the sintering process. Figure 1 , Figure 2 It can be seen that the electrode surface is smooth and defect-free and the internal components are evenly distributed under this component ratio, which fully demonstrates the excellent compatibility of the modified conductive additive with silver powder and glass powder, as well as the role of the technical solution of the present invention in ensuring the density of the electrode.

[0039] Furthermore, the conductive additive undergoes surface modification treatment. The modified conductive additive can form good compatibility with silver powder and glass powder, avoid the formation of pores inside the electrode, ensure the density and conductivity of the electrode, and prevent oxidation of the conductive additive during the sintering process.

[0040] Example 1

[0041] This embodiment provides a method for preparing a silver electrode, which is suitable for ceramic electronic components with high conductivity requirements and moderate cost control. The specific steps are as follows:

[0042] 1. Preparation of glass raw materials: Accurately weigh 200g of glass raw materials according to the mass ratio of SiO2:B2O3:Bi2O3:Na2CO3:Al2O3 = 1:3:4.5:0.5:1. SiO2 is selected as analytical grade powder with a purity ≥99.5%, B2O3 is selected as industrial grade powder with a particle size ≤100μm, and Bi2O3 is selected as electronic grade powder with a purity ≥99.8%. Using anhydrous ethanol as solvent, the raw materials are added to a planetary ball mill at a mass ratio of raw materials:ethanol:zirconium balls = 1:1:4. The ball milling speed is set to 300rpm, and the mixture is milled for 24 hours to ensure thorough and uniform dispersion of the raw materials. The zirconium balls are made of zirconium oxide and have a diameter of 5mm to avoid introducing impurities during the milling process. The uniformly mixed raw material slurry is then... The material is filtered using a plate and frame filter press to remove excess ethanol, and then placed in a forced-air drying oven to dry at a constant temperature of 100℃ for 24 hours to completely remove moisture. After drying, the material is passed through a 100-mesh standard sieve to remove undispersed agglomerated particles, resulting in uniform glass raw material powder. The raw material powder is then placed in a high-temperature muffle furnace and heated to 1000℃ at a heating rate of 5℃ / min for high-temperature melting for 1 hour. After melting, the molten glass is quickly poured into room-temperature distilled water for quenching, allowing the glass to cool rapidly and form irregular glass slag, thus preventing glass crystallization from affecting the subsequent sintering performance of the glass powder.

[0043] 2. Preparation of glass powder: Take the glass slag prepared in step 1, remove surface impurities, and crush it in a planetary ball mill using anhydrous ethanol as solvent at a mass ratio of raw material: ethanol: zirconium balls = 1:1:4. The zirconium balls are divided into three sizes: large, medium, and small, all made of zirconium oxide, with diameters of 15mm, 10mm, and 5mm respectively. The mass ratio of large balls: medium balls: small balls = 1:1:3 can improve crushing efficiency and ensure uniform crushing of the glass slag. The ball mill speed is set to 400 rpm. The glass powder was ball-milled for 12 hours to obtain a uniform glass powder ethanol suspension. The suspension was then filtered using a plate and frame filter press to remove the ethanol. After filtration, the suspension was placed in a forced-air drying oven and dried at a constant temperature of 100℃ for 24 hours. After drying, the glass powder was passed through a 100-mesh standard sieve to obtain SiO2-B2O3-Bi2O3-Na2CO3-Al2O3 glass powder with an average particle size (D50) of 1.5μm. The softening temperature of the glass powder was found to be 450℃, and it exhibited excellent compatibility with silver powder and ceramic substrates.

[0044] 3. Preparation of silver paste: Accurately weigh each raw material according to the mass ratio of silver powder:glass powder:surface-modified nickel powder:organic carrier = 48:18:2:30. The silver powder used is near-spherical electronic-grade silver powder with a diameter ranging from 0.05 to 2.5 μm, a purity ≥99.9%, and a specific surface area of ​​1.2 m². 2 / g; The surface-modified nickel powder is selected from nickel powder modified with silane coupling agent (KH-550) and coated with silver. The particle size is 0.1-1.5μm. After modification, the surface hydrophobicity of the nickel powder is enhanced, which can effectively improve the compatibility with silver powder and glass powder and avoid oxidation during the sintering process of conductive additives; The organic carrier is a mixture of terpineol and ethyl cellulose (terpineol:ethyl cellulose = 95:5, mass ratio), which has good film-forming properties and volatility; The weighed raw materials are put into a high-speed mixer. The rotation speed was set to 1000 rpm, and the mixture was stirred for 5 minutes to ensure that the raw materials were initially mixed evenly. Then, the mixed slurry was fed into a three-roll mill for rolling. The rolling process parameters were strictly controlled as follows: rotation speed 120 rpm, step size 20 μm, maximum gap 80 μm, minimum gap 5 μm, and gap difference between the two rollers 10 μm. After three rolling processes, a uniform, fine, lump-free silver paste with a viscosity of 25000 mPa·s was obtained. The solid content of the silver paste was tested to be 70 wt.%, which meets the requirements for use in screen printing or silver dipping processes.

[0045] 4. Sintering of silver electrodes: Take the silver paste prepared in step 3 and form end electrodes on the surface of the chip element using a silver-dip process. The electrode thickness is controlled to be 10-35 μm. Place the ceramic substrate with the silver paste electrode into a sintering furnace and first hold it at 200℃ for 30 min to remove the volatile components in the organic carrier. Then, raise the temperature to 650℃ at a heating rate of 3℃ / min and sinter at a constant temperature for 5 min. During the sintering process, introduce an air atmosphere to ensure that the organic carrier is fully combusted and decomposed. After sintering, cool it to room temperature at a cooling rate of 2℃ / min to obtain the silver electrode.

[0046] like Figure 3 As shown, the silver electrode prepared in this embodiment has good sintering density, a smooth surface without obvious protrusions or depressions, and a surface roughness Ra≤0.5μm as detected by SEM, with no obvious internal pores. The electrode has a sheet resistance of 3.5mΩ / □ as tested by conductivity performance, and its conductivity is stable. The silver content is 48wt.%, which reduces the cost by about 5% compared to silver electrodes with a silver content ≥50wt.% in the prior art, and all performance characteristics meet the actual application requirements of ceramic electronic components.

[0047] Compare with Example 1

[0048] This comparative example illustrates the role of surface-modified conductive additives (nickel powder) in the preparation of silver electrodes. The difference from Example 1 is that no surface-modified nickel powder is added to the silver paste raw material; all other raw material specifications and preparation process parameters remain the same as in Example 1. The specific steps are as follows:

[0049] 1. Preparation of glass raw materials: The preparation is exactly the same as step 1 in Example 1, that is, SiO2, B2O3 and Bi2O3 raw materials of the same specifications and the same mass ratio are selected, and the same ball milling, pressure filtration, drying, sieving, high-temperature melting and quenching processes are used to obtain glass slag with the same properties, so as to ensure that the glass raw materials do not interfere with the experimental results.

[0050] 2. Preparation of glass powder: The process is exactly the same as step 2 in Example 1, using the same glass slag crushing, pressure filtration, drying and sieving process to obtain SiO2-B2O3-Bi2O3-Na2CO3-Al2O3 glass powder with an average particle size (D50) of 1.5μm. The softening temperature, compatibility and other properties of the glass powder are completely consistent with those in Example 1.

[0051] 3. Preparation of silver paste: The raw materials were accurately weighed according to the mass ratio of silver powder: glass powder: organic carrier = 50:20:30, and the specifications of silver powder, glass powder and organic carrier were exactly the same as in Example 1. The weighed raw materials were put into a high-speed mixer, the speed was set to 1000 rpm and mixed for 5 minutes. Then the mixture was put into a three-roll mill and rolled according to the same rolling process parameters as in Example 1 (speed 120 rpm, step 20 μm, maximum gap 80 μm, minimum gap 5 μm, and gap difference between the two rollers 10 μm) to obtain a uniform silver paste. The viscosity of the silver paste was tested to be 60500 mPa·s and the solid content was 70 wt.%, which was basically consistent with the physicochemical properties of the silver paste in Example 1.

[0052] 4. Sintering of silver electrodes: The process is exactly the same as step 4 in Example 1. The same silver-dip process is used to form electrodes with a thickness of 10-15 μm on the surface of the Al2O3 ceramic substrate. The same heating, holding, sintering and cooling processes are used to ensure that the sintering process does not interfere with the experimental results.

[0053] like Figure 4 As shown, although the silver electrode prepared in this comparative example exhibits good sintering density and no obvious large pores, it suffers from severe glass flotation on the surface. The glass phase accumulates on the electrode surface, forming obvious protrusions and uneven areas. SEM analysis revealed that the electrode surface roughness Ra ≥ 2.0 μm, exceeding the requirements for practical applications. Furthermore, the silver content of this electrode is 50 wt.%, compared to 48 wt.% in Example 1, resulting in a cost increase of approximately 4%. Conductivity testing showed that the sheet resistance of the electrode was 5.5 mΩ / □, slightly higher than that of Example 1. Therefore, adding a small amount of surface-modified nickel powder can effectively improve the sintering condition of the silver electrode, suppress glass flotation, and ensure a smooth electrode surface. It also maintains the electrode's conductivity while reducing the silver content, highlighting the core role of the modified conductive additive in the technical solution of this invention.

[0054] Example 2

[0055] This embodiment provides a method for preparing a silver electrode, suitable for ceramic packaging substrates with high cost control requirements and moderate conductivity requirements. The specific steps are as follows:

[0056] 1. Preparation of glass raw materials: The preparation is exactly the same as step 1 in Example 1, that is, 200g of glass raw materials are weighed according to the mass ratio of SiO2:B2O3:Bi2O3:Na2CO3:Al2O3=1:3:4.5:0.5:1. The same specifications of raw materials are selected, and the same ball milling, pressure filtration, drying, sieving, high-temperature melting and quenching processes are used to obtain glass slag with consistent properties, so as to ensure the stable sintering performance of the glass phase.

[0057] 2. Preparation of glass powder: The process is exactly the same as step 2 in Example 1, using the same glass slag crushing, pressure filtration, drying, and sieving process to obtain SiO2-B2O3-Bi2O3-Na2CO3-Al2O3 glass powder with an average particle size (D50) of 1.5μm. The properties of the glass powder are consistent with those in Example 1, which can effectively ensure the bonding strength with silver powder and modified nickel powder.

[0058] 3. Preparation of silver paste: The raw materials were accurately weighed according to the mass ratio of silver powder:glass powder:surface-modified nickel powder:organic carrier = 25:22:25:27. The silver powder used was spherical electronic-grade silver powder (diameter 0.05–2.5 μm, purity ≥99.9%), the same as in Example 1. The surface-modified nickel powder used was silane coupling agent modified nickel powder (particle size 0.1–1.0 μm), the same as in Example 1, with a significantly increased silver coating to replace more silver powder and reduce costs. The organic carrier used was the same as in Example 1. An oleyl alcohol-ethyl cellulose mixture system was used to ensure the film-forming properties and volatility of the silver paste. All raw materials were fed into a high-speed mixer at 1000 rpm for 5 minutes to ensure thorough mixing of the silver powder, glass powder, modified nickel powder, and organic carrier. The mixture was then fed into a three-roll mill and rolled using the same rolling parameters as in Example 1. After four rolling passes, a uniform, fine, and lump-free silver paste with a viscosity of 60,000 mPa·s was obtained. Testing showed that the solid content of the silver paste was 73 wt.%, meeting the requirements for silvering processes, and exhibiting good dispersibility with no sedimentation.

[0059] 4. Sintering of silver electrodes: Take the silver paste prepared in step 3 and form electrodes on the surface of Al2O3 ceramic encapsulation substrate using a silver-dip process. The electrode thickness is controlled to be 12-38 μm. Place the substrate with silver paste electrodes into a sintering furnace and first hold it at 200℃ for 30 min to remove the organic carrier. Then, raise the temperature to 650℃ at a heating rate of 3℃ / min and sinter at a constant temperature for 5 min. During the sintering process, introduce an air atmosphere to ensure that the organic carrier is fully combusted. After sintering, cool it to room temperature at a cooling rate of 2℃ / min to obtain the silver electrodes.

[0060] like Figure 5 As shown, the silver electrode prepared in this embodiment exhibits good sintering density, a smooth surface without obvious protrusions or depressions, and a surface roughness Ra ≤ 0.6 μm as determined by SEM. The internal components are uniformly distributed without significant pores or defects. Conductivity testing shows that the electrode's sheet resistance is 3.8 mΩ / □, slightly higher than in Example 1, but still meets the conductivity requirements for the end electrode of a chip element. With a silver content of only 25 wt.%, the cost is reduced by approximately 40% compared to silver electrodes with a silver content ≥ 50 wt.% in the prior art, and by approximately 35% compared to Example 1, achieving a significant cost reduction while ensuring excellent electrode quality, fully meeting practical application requirements.

[0061] Example 3

[0062] This embodiment provides a method for preparing a silver electrode, suitable for ceramic electronic components with extremely high cost control requirements and conductivity requirements that meet basic usage needs. It is the embodiment with the lowest silver content in this invention. The specific steps are as follows:

[0063] 1. Preparation of glass raw materials: The preparation is exactly the same as step 1 in Example 1, that is, 200g of glass raw materials are weighed according to the mass ratio of SiO2:B2O3:Bi2O3:Na2CO3:Al2O3=1:3:4.5:0.5:1. The same specifications of raw materials are selected, and the same ball milling, pressure filtration, drying, sieving, high-temperature melting and quenching processes are used to obtain glass slag with stable performance, ensuring that the glass phase can play a good sintering promoting role and make up for the impact of the reduction of silver content on the density of the electrode.

[0064] 2. Preparation of glass powder: The preparation is exactly the same as step 2 in Example 1, using the same glass slag crushing, pressure filtration, drying and sieving process to obtain SiO2-B2O3-Bi2O3-Na2CO3-Al2O3 glass powder with an average particle size (D50) of 1.5μm. The glass powder has excellent compatibility with silver powder and modified nickel powder, which can effectively improve the bonding strength of the electrode.

[0065] 3. Preparation of silver paste: Each raw material was precisely weighed according to the mass ratio of silver powder:glass powder:surface-modified nickel powder:organic carrier = 15:22:35:27. The silver powder used was the same spherical electronic-grade silver powder as in Example 1, but its addition was reduced to a minimum of 15 wt.%. The surface-modified nickel powder was the same silane coupling agent modified and silver-coated nickel powder as in Example 1, with its addition increased to 35 wt.%, making it the main component replacing silver powder in this example. To ensure the dispersibility and stability of the silver paste, an additional 2 minutes of mixing was added during the mixing process. The organic carrier used was the same terpineol-ethyl cellulose mixture as in Example 1 to ensure good film-forming properties of the silver paste. All raw materials were fed into a high-speed mixer at 1000 rpm for 7 minutes to ensure thorough and uniform dispersion. Subsequently, the paste was fed into a three-roll mill and rolled using the same rolling process parameters as in Example 1. After five rolling passes, a uniform, fine, and lump-free silver paste with a viscosity of 66000 mPa·s was obtained. Testing showed that the solid content of the silver paste was 73 wt.%, with good dispersibility, meeting the requirements for silver plating processes.

[0066] 4. Sintering of silver electrodes: Take the silver paste prepared in step 3 and form electrodes on the surface of Al2O3 ceramic components using a silver-dip process. The electrode thickness is controlled to be 15-20 μm. Place the components with silver paste electrodes into a sintering furnace and first hold them at 200℃ for 30 min to completely remove the organic carrier. Then, raise the temperature to 650℃ at a heating rate of 3℃ / min and sinter at a constant temperature for 5 min. During the sintering process, introduce an air atmosphere to ensure that the organic carrier is fully combusted and decomposed. After sintering, cool to room temperature at a cooling rate of 2℃ / min to obtain the silver electrodes.

[0067] like Figure 6 As shown, the silver electrode prepared in this embodiment has moderate sintering density. SEM analysis revealed a small number of micropores (porosity ≤ 5%) inside the electrode, but the surface is smooth without obvious protrusions or depressions, and the surface roughness Ra ≤ 0.8 μm, which does not affect the actual use of the electrode. Conductivity testing showed that the sheet resistance of the electrode was 3.9 mΩ / □, meeting the basic conductivity requirements of ceramic electronic components. The silver content was only 15 wt.%, which is the lowest silver content achievable by this invention. Compared with silver electrodes with a silver content ≥ 50 wt.% in the prior art, the cost is reduced by about 60%, and compared with Example 2, the cost is further reduced by about 15%. This completely solves the technical problem that it is difficult to further reduce the silver content in the prior art, achieving maximum cost savings while ensuring the basic performance of the electrode.

[0068] The examples provided in this invention are not intended to limit the implementation. Those skilled in the art will recognize that various variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, and any obvious variations or modifications derived therefrom are still within the scope of this invention.

Claims

1. A method for preparing a silver electrode, characterized in that, Includes the following steps: 1) Preparation of glass raw materials: Weigh each raw material according to the mass ratio, and ball mill them together for 24 hours with ethanol as solvent at a ratio of glass:ethanol:zirconium balls = 1:1:4; after pressing and filtering the uniformly mixed raw materials, dry them at 100℃ for 24 hours, and pass them through a 100-mesh sieve to obtain raw material powder; melt the raw material powder at a high temperature of 1400-1600℃ for 0.5-2 hours, and quench the glass melt in distilled water to obtain glass slag; 2) Preparation of glass powder: Take the glass slag prepared in step 1) and crush it by planetary ball milling with ethanol as solvent at a ratio of glass slag: ethanol: zirconium balls = 1:1:4; suspend the crushed glass powder in ethanol and pressurize it by hydraulic filtration, dry it at 100℃ for 24h, and pass it through a 200-mesh sieve to obtain glass powder with an average particle size of 0.5~3.0μm. 3) Preparation of silver paste: Weigh each raw material according to the mass percentage. The raw materials include 10-60 wt.% silver powder, 3-20 wt.% glass powder prepared in step 2), 3-40 wt.% conductive additives, and 15-30 wt.% organic carrier. Mix the weighed raw materials in a high-speed mixer at a speed of 800-2000 rpm for 10-20 minutes. Then, roll the uniformly mixed paste with three rollers to obtain a uniform silver paste. 4) Sintering of silver electrodes: Take the silver paste prepared in step 3) and form electrodes on the surface of the component by screen printing or silver dipping process. Then, heat the electrode to 500-750℃ at a heating rate of 1-10℃ / min and sinter for 1-60min. After cooling, the silver electrode is obtained. The internal elements of the silver electrode are analyzed and found to contain silver, glass and conductive additives.

2. The method for preparing a silver electrode according to claim 1, characterized in that, In step 1), the glass raw material is made of SiO2, B2O3, Bi2O3, Na2CO3, and Al2O3.

3. The method for preparing a silver electrode according to claim 1, characterized in that, In step 1), the diameter of the zirconium ball is 5 mm.

4. The method for preparing a silver electrode according to claim 1, characterized in that, In step 2), the zirconium balls are divided into three sizes: large, medium, and small, with diameters of 15mm, 10mm, and 5mm respectively. The ratio of large ball to medium ball to small ball is 1:1:

3.

5. The method for preparing a silver electrode according to claim 1, characterized in that, In step 3), the silver powder is spherical with a diameter in the range of 0.05 to 2.5 μm.

6. The method for preparing a silver electrode according to claim 1, characterized in that, In step 3), the conductive additive is one or more of the following: surface-modified nickel powder, tungsten powder, molybdenum powder, and copper powder.

7. The method for preparing a silver electrode according to claim 1, characterized in that, In step 3), the organic carrier is a mixture of terpineol and ethyl cellulose.

8. The method for preparing a silver electrode according to claim 1, characterized in that, In step 3), the rolling process parameters are: rotation speed 100-150 rpm, step size 10-20 μm, maximum gap 80-100 μm, minimum gap 5-15 μm, and gap difference between the two rollers 10-20 μm.

9. The method for preparing a silver electrode according to claim 1, characterized in that, In step 4), the silver electrode contains silver, glass, and conductive additives, wherein the electrode contains 12-72 wt.% silver powder, 4-24 wt.% glass powder prepared in step 2), and 4-48 wt.% conductive additives.

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