A micron-sized silver powder, its preparation method and application

Abstract

The present invention relates to the technical field of silver powder preparation, and specifically discloses a micron-sized silver powder, a preparation method thereof and an application. A preparation method of a micron-sized silver powder comprises first dissolving 40-60 parts of silver nitrate in 180-220 parts of water, adding 40-60 parts of 25% (w / w) ammonia water to form a reaction solution, then dissolving 3-4 parts of glucose, 3-5 parts of hydroxylamine hydrochloride and 7-8 parts of triethanolamine in 180-220 parts of water, adding 5-10 parts of sodium hydroxide to adjust the pH value to form a reducing solution; then mixing the reducing solution and the reaction solution to carry out a reduction reaction; then continuously adding sodium polymethacrylate and N,N-dimethylstearamide, and finally filtering, washing and drying to obtain the micron-sized silver powder. The internal electrode conductive silver paste prepared from the micron-sized silver powder of the present application has good printing characteristics during the printing process and good co-firing compatibility with the dielectric layer during the firing process.

Description

Technical Field

[0001] The present invention relates to the technical field of silver powder preparation, and particularly to a micron-sized silver powder, a preparation method thereof, and an application thereof. Background Art

[0002] In the manufacture of stacked products such as stacked inductors and beads, inner electrode conductive silver paste is mainly used as a key material. The inner electrode conductive silver paste usually consists of conductive silver powder, resin, solvent, and various additives. Through specific printing processes such as screen printing, gravure offset printing, or lithography, the silver paste is printed on the dielectric film in a preset pattern. Subsequently, through a series of complex processes such as stacking, hydrostatic pressure, cutting, firing, end burning, electroplating, etc., products such as stacked inductors and beads are finally formed. In this series of processes, the performance of the inner electrode conductive silver paste, especially its printing characteristics, co-firing characteristics with the dielectric layer, and firing resistance, becomes a key factor affecting the quality of products such as stacked inductors and beads.

[0003] As the core component in the inner electrode conductive silver paste, the firing resistance and dispersibility of silver powder directly determine the overall performance of the inner electrode conductive silver paste. Among them, the firing resistance of silver powder directly affects the change curve of the firing shrinkage of the prepared inner electrode conductive silver paste, and further affects the firing match between the inner electrode formed by the inner electrode conductive silver paste and the dielectric layer formed by the dielectric. If the match is inappropriate, the inductor is very likely to have internal cracks or even cracks. In addition, the dispersibility of silver powder directly affects the printing effect of the inner electrode conductive silver paste. Silver powder with poor dispersibility results in poor printing performance of the prepared inner electrode conductive silver paste, and it is extremely easy to have problems such as poor electrode fullness and even printing defects such as lotus roots on the electrodes. With the development of the miniaturization trend of electronic components, higher requirements are put forward for the dispersibility and firing resistance of silver powder. However, there is often a contradiction between the dispersibility and firing resistance of silver powder on the current market: silver powder with good dispersibility has relatively poor firing resistance due to its high activity; while silver powder with good firing resistance often has poor dispersibility, which affects the printing effect. This contradiction severely restricts the further improvement of the performance of the inner electrode conductive silver paste and has also become a key technical problem in the manufacture of stacked products such as stacked inductors and beads.

[0004] Therefore, it is necessary to develop a silver powder that has both good dispersibility and good firing resistance, further improve the performance of the inner electrode conductive silver paste, further improve the performance of products such as stacked inductors and beads, and promote the miniaturization process of electronic components. Summary of the Invention

[0005] In order to develop a silver powder with both good dispersibility and excellent firing resistance, the present application provides a micron-sized silver powder, a preparation method thereof, and an application. By selecting specific reducing agents and dispersants and through the synergistic cooperation of the reducing agents and dispersants, the present application realizes the uniform dispersion and stable growth of silver powder during the preparation process, thereby preparing a micron-sized silver powder with a high sphericity and a uniform particle size distribution, and thus preparing a micron-sized silver powder with both good dispersibility and good firing resistance. The inner electrode conductive silver paste prepared from the micron-sized silver powder of the present application has good printing characteristics during the printing process, and at the same time has good co-firing compatibility with the dielectric layer during the firing process, effectively avoiding the problems of internal cracking or cracking between the inner electrode and the dielectric layer, and not easily showing problems such as poor electrode fullness or lotus root-shaped printing defects, further improving the overall performance of products such as multilayer inductors and beads.

[0006] In the first aspect, the preparation method of a micron-sized silver powder provided by the present application adopts the following technical solution:

[0007] A preparation method of a micron-sized silver powder includes the following steps:

[0008] Step 1: Based on the mass parts of the reaction solution, dissolve 40 - 60 parts of silver nitrate in 180 - 220 parts of water, and add 40 - 60 parts of 25% (w / w) ammonia water to prepare a reaction solution.

[0009] Step 2: Based on the mass parts of the reducing solution, dissolve 3 - 4 parts of glucose, 3 - 5 parts of hydroxylamine hydrochloride, and 7 - 8 parts of triethanolamine in 180 - 220 parts of water, and add 5 - 10 parts of sodium hydroxide to adjust the pH value to prepare a reducing solution.

[0010] Step 3: Under a stirring state, completely add the reducing solution to the reaction solution for a reduction reaction.

[0011] Step 4: After the addition of the reducing solution is completed, continue to add sodium polymethacrylate and N,N-dimethylstearamide, and continue to stir evenly to obtain a dispersion liquid. The mass ratio of silver nitrate, sodium polymethacrylate, and N,N-dimethylstearamide is 100:(0.31 - 0.64):(0.19 - 0.5).

[0012] Step 5: Filter, wash, and dry the dispersion liquid to obtain a micron-sized silver powder.

[0013] In the above technical solution, the present application uses a reducing agent composed of a compound of glucose, hydroxylamine hydrochloride and triethanolamine, and a dispersant composed of a compound of sodium polymethacrylate and N,N-dimethylstearamide. Through the synergistic effect of the specific reducing agent and dispersant, the uniform dispersion and stable growth of micron-sized silver powder are achieved. Such micron-sized silver powder not only has good dispersibility but also has good burn resistance. In the reduction reaction, the compound use of glucose, hydroxylamine hydrochloride and triethanolamine not only improves the reduction efficiency but also helps to control the particle size and shape of the silver powder; the addition of sodium polymethacrylate and N,N-dimethylstearamide, in cooperation with the reducing agent, further improves the dispersibility and stability of the silver powder, helps to prevent the silver powder from agglomerating during the subsequent drying and firing processes, thereby maintaining the dispersibility and uniformity of the silver powder. Through this synergistic effect, the finally obtained micron-sized silver powder has a high sphericity and a uniform particle size distribution. Such micron-sized silver powder has lower surface activity and higher dispersibility, and has both good dispersibility and good burn resistance. It can exhibit excellent printing characteristics and firing matching properties in the internal electrode conductive silver paste. The prepared internal electrode conductive silver paste is not only suitable for screen printing in the multilayer inductor, helps to improve the electrode fullness during the printing process, reduces printing defects, but also can have good matching performance with the dielectric firing of the inductor product under the long-term firing condition of 900 °C. This further improves the performance of products such as multilayer inductors and magnetic beads, and promotes the miniaturization process of electronic components.

[0014] Preferably, in step 2, sodium hydroxide is added to adjust the pH value to the range of 13 - 14. After adding sodium hydroxide, it is stirred at 50 - 150 rpm for 15 - 30 min to obtain a reduction solution.

[0015] In the above technical solution, by adjusting the pH value to a specific range, the present application can ensure that the activity of the reducing agent is optimized, making the particle size distribution of the silver powder more uniform, thereby improving the uniformity and reaction efficiency of the silver powder, and further optimizing the dispersibility and sphericity of the silver powder. At the same time, under the adjustment of the pH value, the occurrence of side reactions is reduced, ensuring the purity and quality of the silver powder.

[0016] Preferably, in step 3, the mass ratio of the reduction solution to the reaction solution is 1:(1 - 1.5).

[0017] In the above technical solution, by controlling the mass ratio of the reduction solution to the reaction solution within the range of 1:(1 - 1.5), the present application can ensure the full progress of the reduction reaction, avoid the residue of unreacted silver nitrate in the reaction solution, thereby improving the yield and purity of the silver powder. At the same time, it helps to form uniform silver powder particles, reduce the agglomeration phenomenon, so that the finally obtained micron-sized silver powder has better dispersibility and burn resistance.

[0018] Preferably, step 3 is as follows: Adjust the temperatures of the reducing solution and the reaction solution to 30-40°C respectively, and then, under the stirring state of 50-150 rpm, add the reducing solution to the reaction solution completely within 1-10 minutes for the reduction reaction.

[0019] In the above technical solution, in the present application, by controlling the temperatures of the reducing solution and the reaction solution within the range of 30-40°C, and under the stirring speed of 50-150 rpm, adding the reducing solution to the reaction solution within 1-10 minutes, the smooth progress of the reduction reaction can be ensured, which is helpful for forming silver powder particles with uniform particle size distribution and higher sphericity, and further improving the dispersibility and burn resistance of the micron-sized silver powder.

[0020] Preferably, in step 4, continuing to stir evenly means continuously stirring at 50-150 rpm for 30-40 minutes at a temperature of 30-40°C.

[0021] In the above technical solution, by controlling the dispersion liquid to continuously stir at a stirring speed of 50-150 rpm for 30-40 minutes at a temperature of 30-40°C, the full mixing of sodium polymethacrylate and N,N-dimethylstearamide with the silver powder particles can be ensured, and the full modification of the surface of the silver powder by sodium polymethacrylate and N,N-dimethylstearamide can be ensured, so as to further improve the dispersibility and stability of the silver powder, further prevent the agglomeration phenomenon of the silver powder during the subsequent drying and firing processes, and maintain the dispersibility and uniformity of the silver powder.

[0022] Preferably, step 5 is as follows: After filtering, washing, and drying the dispersion liquid, wash it twice with banana water, and then obtain micron-sized silver powder after drying.

[0023] In the above technical solution, in the present application, by washing the micron-sized silver powder twice with banana water after filtering, washing, and drying, the organic matters and impurities remaining on the surface of the micron-sized silver powder can be removed better, the conductivity of the micron-sized silver powder can be further improved, and the dispersibility and printing characteristics of the micron-sized silver powder in the internal electrode conductive silver paste can be further improved.

[0024] Preferably, the median particle size of the micron-sized silver powder is below 3.0 μm.

[0025] In the above technical solution, in the present application, by controlling the median particle size of the micron-sized silver powder to be below 3.0 μm, the micron-sized silver powder can better combine with the dielectric material, reduce the shrinkage and cracks after firing, and ensure that the micron-sized silver powder is suitable for the internal electrode conductive silver paste for printing narrow-width lines, especially suitable for printing ultra-fine lines with a wire diameter of about 15 μm.

[0026] In the second aspect, a micron-sized silver powder provided by the present application adopts the following technical solution:

[0027] A micron-sized silver powder is prepared by using the preparation method of the micron-sized silver powder described in the first aspect.

[0028] In the above technical solution, the micron-sized silver powder prepared in this application has a uniform particle size distribution, high sphericity, good dispersibility and fire resistance, has good fluidity during the screen printing process, can significantly reduce printing defects, and is suitable for the manufacture of various electronic components.

[0029] In the third aspect, an application of a micron-sized silver powder provided in this application adopts the following technical solution:

[0030] An application of a micron-sized silver powder is used to prepare an inner electrode conductive silver paste.

[0031] In the above technical solution, the application of the micron-sized silver powder prepared in this application in the inner electrode conductive silver paste not only improves the electrode fullness during the printing process, but also has excellent matching performance with the inductor product medium under high-temperature firing conditions, significantly improving the performance of electronic components such as multilayer inductors and beads. In addition, due to the high dispersibility and good fire resistance of the micron-sized silver powder, the inner electrode conductive silver paste has better printing characteristics during the printing process, thus further promoting the miniaturization and high performance of electronic components.

[0032] Preferably, the inner electrode conductive silver paste includes the following components: 4wt%-6wt% ethyl cellulose, 8wt%-12wt% terpineol, 80wt%-90wt% micron-sized silver powder.

[0033] In summary, this application includes at least one of the following beneficial technical effects:

[0034] 1. This application provides a preparation method of a micron-sized silver powder. By optimizing the formulations of the reducing agent and the dispersant, specifically selecting a reducing agent composed of a compound of glucose, hydroxylamine hydrochloride and triethanolamine, and a dispersant composed of a compound of sodium polymethacrylate and N,N-dimethylstearamide, through the synergistic effect of such a reducing agent and a dispersant, the uniformity of the particle size distribution and high sphericity of the micron-sized silver powder are ensured, the good dispersibility and fire resistance of the micron-sized silver powder are achieved, and such a micron-sized silver powder is suitable for high-temperature firing at 900°C.

[0035] 2. By adjusting the pH value to a specific range, this application reduces the occurrence of side reactions, ensures the purity and quality of the silver powder, and further optimizes the dispersibility and sphericity of the silver powder.

[0036] 3. By controlling the mass ratio of the reducing solution to the reaction solution within a certain range, this application ensures the full progress of the reduction reaction, improves the yield and purity of the silver powder, and at the same time helps to form uniform silver powder particles and reduce the agglomeration phenomenon.

[0037] 4. By controlling the median particle size of the micron-sized silver powder to be below 3.0 μm, this application ensures good bonding between the silver powder and the dielectric material, reduces shrinkage and cracks after firing, is suitable for screen printing processes, especially for printing with a finer wire diameter of about 15 μm. This significantly improves the performance of electronic components such as multilayer inductors and beads, and promotes the miniaturization and high performance of electronic components. Description of the Drawings

[0038] Figure 1 It is the SEM image of the micron-sized silver powder of Example 1.

[0039] Figure 2 It is the SEM image of the micron-sized silver powder of Example 2.

[0040] Figure 3 It is the SEM image of the micron-sized silver powder of Example 3.

[0041] Figure 4 It is the SEM image of the micron-sized silver powder of Comparative Example 1.

[0042] Figure 5 It is the SEM image of the micron-sized silver powder of Comparative Example 2.

[0043] Figure 6 It is the SEM image of the micron-sized silver powder of Comparative Example 3.

[0044] Figure 7 It is the SEM image of the micron-sized silver powder of Comparative Example 4.

[0045] Figure 8 It is the SEM image of the micron-sized silver powder of Comparative Example 5.

[0046] Figure 9 It is the VPSD image of the internal electrode conductive silver paste of Application Example 1.

[0047] Figure 10 It is the VPSD image of the internal electrode conductive silver paste of Application Example 2.

[0048] Figure 11 It is the VPSD image of the internal electrode conductive silver paste of Application Example 3.

[0049] Figure 12 It is the VPSD image of the internal electrode conductive silver paste of Comparative Application Example 1.

[0050] Figure 13 It is the VPSD image of the internal electrode conductive silver paste of Comparative Application Example 2.

[0051] Figure 14 It is the VPSD image of the internal electrode conductive silver paste of Comparative Application Example 3.

[0052] Figure 15It is the VPSD diagram of the internal electrode conductive silver paste for Comparative Application Example 4.

[0053] Figure 16 It is the VPSD diagram of the internal electrode conductive silver paste for Comparative Application Example 5.

[0054] Figure 17 It is the TMA firing shrinkage curve of the internal electrode conductive silver paste for Application Example 1.

[0055] Figure 18 It is the TMA firing shrinkage curve of the internal electrode conductive silver paste for Application Example 2.

[0056] Figure 19 It is the TMA firing shrinkage curve of the internal electrode conductive silver paste for Application Example 3.

[0057] Figure 20 It is the TMA firing shrinkage curve of the internal electrode conductive silver paste for Comparative Application Example 1.

[0058] Figure 21 It is the TMA firing shrinkage curve of the internal electrode conductive silver paste for Comparative Application Example 2.

[0059] Figure 22 It is the TMA firing shrinkage curve of the internal electrode conductive silver paste for Comparative Application Example 3.

[0060] Figure 23 It is the TMA firing shrinkage curve of the internal electrode conductive silver paste for Comparative Application Example 4.

[0061] Figure 24 It is the TMA firing shrinkage curve of the internal electrode conductive silver paste for Comparative Application Example 5.

[0062] Figure 25 It is the printing effect diagram of the internal electrode conductive silver paste for Application Example 1.

[0063] Figure 26 It is the printing effect diagram of the internal electrode conductive silver paste for Application Example 2.

[0064] Figure 27 It is the printing effect diagram of the internal electrode conductive silver paste for Application Example 3.

[0065] Figure 28 It is the printing effect diagram of the internal electrode conductive silver paste for Comparative Application Example 1.

[0066] Figure 29 It is the printing effect diagram of the internal electrode conductive silver paste for Comparative Application Example 2.

[0067] Figure 30 It is the printing effect diagram of the internal electrode conductive silver paste for Comparative Application Example 3.

[0068] Figure 31It is the printing effect diagram of the internal electrode conductive silver paste in Comparative Application Example 4.

[0069] Figure 32 It is the printing effect diagram of the internal electrode conductive silver paste in Comparative Application Example 5. Detailed implementation manners

[0070] To better illustrate the purpose, technical solution and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0071] Embodiment 1

[0072] A preparation method of micron-sized silver powder includes the following steps:

[0073] Step 1: Dissolve 400 g of silver nitrate in 1800 g of water, add 400 g of 25% (w / w) ammonia water to prepare a reaction solution.

[0074] Step 2: Dissolve 40 g of glucose, 30 g of hydroxylamine hydrochloride and 80 g of triethanolamine in 1800 g of water, adjust the pH value to 13, add 50 g of sodium hydroxide, and stir at 80 rpm for 30 min to obtain a reducing solution.

[0075] Step 3: Adjust the temperatures of 2000 g of the reducing solution and 2600 g of the reaction solution to 30 °C respectively, and then, under the stirring state of 50 rpm, add the reducing solution completely into the reaction solution within 5 min to carry out a reduction reaction.

[0076] Step 4: After the addition of the reducing solution is completed, continue to add 1.24 g of sodium polymethacrylate and 0.76 g of N,N-dimethylstearamide, and continuously stir at 30 °C and 50 rpm for 40 min to obtain a dispersion.

[0077] Step 5: Filter, wash and dry the dispersion, and then wash it twice with banana oil, and dry it to obtain micron-sized silver powder with a median particle size (D50) of less than 3.0 μm.

[0078] Embodiment 2

[0079] A preparation method of micron-sized silver powder, which is different from Embodiment 1, includes the following steps:

[0080] Step 1: Dissolve 500 g of silver nitrate in 2000 g of water, add 500 g of 25% (w / w) ammonia water to prepare a reaction solution.

[0081] Step 2: Dissolve 35 g of glucose, 45 g of hydroxylamine hydrochloride and 70 g of triethanolamine in 2000 g of water, adjust the pH value to 13.5, add 70 g of sodium hydroxide, and stir at 100 rpm for 25 min to obtain a reducing solution.

[0082] Step 3: Adjust the temperatures of 2220 g of the reducing solution and 3000 g of the reaction solution to 35°C respectively. Then, under the stirring condition of 100 rpm, add the reducing solution to the reaction solution completely within 8 min to carry out the reduction reaction.

[0083] Step 4: After the addition of the reducing solution is completed, continue to add 2.55 g of sodium polymethacrylate and 1.8 g of N,N-dimethylstearamide, and continuously stir at 35°C and 100 rpm for 35 min to obtain a dispersion liquid.

[0084] Step 5: After filtering, washing, and drying the dispersion liquid, wash it twice with banana oil, and then dry it to obtain micron-sized silver powder with a median particle size (D50) of less than 3.0 μm.

[0085] Example 3

[0086] A preparation method of micron-sized silver powder, which is different from Example 1 and includes the following steps:

[0087] Step 1: Dissolve 600 g of silver nitrate in 2200 g of water, add 600 g of 25% (w / w) ammonia water to prepare a reaction solution.

[0088] Step 2: Dissolve 30 g of glucose, 50 g of hydroxylamine hydrochloride, and 75 g of triethanolamine in 2200 g of water, adjust the pH value to 14, add 90 g of sodium hydroxide, and then stir at 150 rpm for 15 min to obtain a reducing solution.

[0089] Step 3: Adjust the temperatures of 2445 g of the reducing solution and 3400 g of the reaction solution to 40°C respectively. Then, under the stirring condition of 150 rpm, add the reducing solution to the reaction solution completely within 3 min to carry out the reduction reaction.

[0090] Step 4: After the addition of the reducing solution is completed, continue to add 3.84 g of sodium polymethacrylate and 3 g of N,N-dimethylstearamide, and continuously stir at 40°C and 150 rpm for 30 min to obtain a dispersion liquid.

[0091] Step 5: After filtering, washing, and drying the dispersion liquid, wash it twice with banana oil, and then dry it to obtain micron-sized silver powder with a median particle size (D50) of less than 3.0 μm.

[0092] Comparative Example 1

[0093] A preparation method of micron-sized silver powder, which is different from Example 1 in that ascorbic acid is used to replace glucose in equal amount in Step 2.

[0094] Comparative Example 2

[0095] A preparation method of micron-sized silver powder, which is different from Example 1 in that hydroxylamine sulfate is used to replace hydroxylamine hydrochloride in equal amount in Step 2.

[0096] Comparative Example 3

[0097] A method for preparing micron-sized silver powder, which is different from Example 1 in that triethanolamine is replaced with ethanolamine in equal amount in Step 4.

[0098] Comparative Example 4

[0099] A method for preparing micron-sized silver powder, which is different from Example 1 in that sodium polymethacrylate is replaced with polyvinylpyrrolidone in equal amount in Step 4.

[0100] Comparative Example 5

[0101] A method for preparing micron-sized silver powder, which is different from Example 1 in that N,N-dimethylstearamide is replaced with oleic amine in equal amount in Step 4.

[0102] Application Example 1

[0103] An internal electrode conductive silver paste, comprising the following components: 5 g of ethyl cellulose, 10 g of terpineol, and 85 g of micron-sized silver powder.

[0104] Among them, the internal electrode conductive silver paste is prepared by the following method:

[0105] Ingredient preparation - Dispersion - Slurry rolling - Filtration - Stirring - Semi-finished product inspection - Adjustment - Finished product detection - Packaging and warehousing.

[0106] Among them, the micron-sized silver powder is prepared from Example 1.

[0107] Application Example 2

[0108] An internal electrode conductive silver paste, which is different from Application Example 1 in that the micron-sized silver powder is prepared from Example 2.

[0109] Application Example 3

[0110] An internal electrode conductive silver paste, which is different from Application Example 1 in that the micron-sized silver powder is prepared from Example 3.

[0111] Comparative Application Example 1

[0112] An internal electrode conductive silver paste, which is different from Application Example 1 in that the micron-sized silver powder is prepared from Comparative Example 1.

[0113] Comparative Application Example 2

[0114] An internal electrode conductive silver paste, which is different from Application Example 1 in that the micron-sized silver powder is prepared from Comparative Example 2.

[0115] Comparative Application Example 3

[0116] An internal electrode conductive silver paste, different from Application Example 1, is that the micron-sized silver powder is prepared from Comparative Example 3.

[0117] Comparative Application Example 4

[0118] An internal electrode conductive silver paste, different from Application Example 1, is that the micron-sized silver powder is prepared from Comparative Example 4.

[0119] Comparative Application Example 5

[0120] An internal electrode conductive silver paste, different from Application Example 1, is that the micron-sized silver powder is prepared from Comparative Example 5.

[0121] Performance verification

[0122] 1. The micron-sized silver powders prepared in Examples 1-3 and Comparative Examples 1-5 were observed under an electron microscope respectively, and the electron microscope images are as shown in the appendix. Figures 1 - 8 as follows.

[0123] Specifically, by comparing and observing the appendix Figures 1 - 8 , it can be seen that: for the micron-sized silver powders prepared in Examples 1-3, the particle distribution is uniform, the surface is smooth, the sphericity is high, and the dispersibility is good, which is suitable for the screen printing process. Therefore, the printed pattern is full and there are no jointed segments. While for the micron-sized silver powders in Comparative Examples 1-5, the surface is not smooth enough, or the dispersibility is poor, or the sphericity is bad.

[0124] 2. The tapped densities of the micron-sized silver powders prepared in Examples 1-3 and Comparative Examples 1-5 were detected. The detection method is as follows: a 10 mL graduated cylinder, 20 g of silver powder sample, vibrate evenly 2000 times, and calculate the volume of the silver powder after vibration to obtain the tapped density. The tapped density ρ = the mass of the silver powder 20 g / the volume V (mL) after vibration.

[0125] The above detection results are shown in Table 1.

[0126] Table 1:

[0127] Group Tap density ρ (g / mL) Example 1 7.62 Example 2 7.21 Example 3 7.13 Comparative Example 1 3.32 Comparative Example 2 5.01 Comparative Example 3 4.35 Comparative Example 4 4.61 Comparative Example 5 4.15

[0128] Specifically, by analyzing the tapped densities ρ of Examples 1-3 and Comparative Examples 1-5, it can be seen that: the tapped densities of Examples 1-3 reached above 7 g / mL, while those of Comparative Examples 1-5 were basically less than 5 g / mL.

[0129] 3. The VPSD of the internal electrode conductive silver pastes of Application Examples 1-3 and Comparative Application Examples 1-5 was detected. Specifically, the median particle size (D50) of the silver powder was detected. The specific detection results are shown in the appendix. Figures 9 - 16 as follows.

[0130] Specifically comparing and observing the VPSD diagrams of Application Examples 1-3 and Comparative Application Examples 1-5, it can be seen that the micron-sized silver powder in Application Examples 1-3 has good dispersibility and more uniform particle sizes, making it more suitable for printing electrodes.

[0131] 4. Conduct a burn resistance test on the internal electrode conductive silver pastes of Application Examples 1-3 and Comparative Application Examples 1-5. Dry the samples at 125°C, grind them, and make samples about 1-2 mm thick and 3 mm in diameter, and then conduct tests using a TMA analyzer. The TMA analyzer used in this experiment is of the Mettler model. The specific test results are shown in the appendix Figures 17 - 24 。

[0132] Specifically comparing and observing the TMA firing shrinkage curves of Application Examples 1-3 and Comparative Application Examples 1-5, it can be seen that the starting temperature points of rapid shrinkage of the internal electrode conductive silver pastes in Application Examples 1-3 and Comparative Application Example 1 are approximately around 700°C. For the internal electrode conductive silver pastes in Comparative Application Examples 2-5, the starting temperature points of rapid shrinkage are basically around 370°C, and then they keep shrinking without a plateau period, indicating that the activity of such internal electrode conductive silver pastes is too high and the burn resistance is poor. Generally, the temperature points of rapid shrinkage during the firing process of the inductive dielectric material co-fired with silver electrodes are also around 700°C, and before sintering, the strength of the dielectric is very low. If the internal electrode conductive silver paste shrinks rapidly prematurely, it is likely to cause mismatched shrinkage between the electrode and the dielectric, resulting in interlayer cracking of the product. Therefore, the activity and burn resistance of silver powder also have a great impact on the use of internal electrode conductive silver pastes. The micron-sized silver powder used in Application Examples 1-3 and Comparative Application Example 1 has good burn resistance and meets the firing conditions of the internal electrode conductive silver paste, while the micron-sized silver powder used in Comparative Application Examples 2-5 has high activity and poor burn resistance, and is not very suitable for the firing conditions of the internal electrode conductive silver paste.

[0133] 5. Compare the printing effects of the internal electrode conductive silver pastes of Application Examples 1-3 and Comparative Application Examples 1-5. The specific printing effect diagrams are shown in the appendix Figures 25 - 32 。

[0134] Specifically comparing and observing the printing effect diagrams of Application Examples 1-3 and Comparative Application Examples 1-5, it can be seen that the printed electrodes in Application Examples 1-3 are uniform, plump, with clear patterns and strong three-dimensional senses. For Comparative Application Example 1, it can be seen that Figure 28 the marked square is the phenomenon of "lotus root joints", which indicates that the printed electrodes of the internal electrode conductive silver paste in Comparative Application Example 1 have poor uniformity, serious "lotus root joints", and are not plump enough, which may have a greater adverse impact on the electrical performance of the later products. Similarly, the printed electrodes of the internal electrode conductive silver pastes in Comparative Application Examples 2-5 also show the phenomenon of "lotus root joints". This proves that the internal electrode conductive silver pastes in Application Examples 1-3 are more suitable for printing electrodes.

[0135] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A method for preparing micron-sized silver powder, characterized in that: The following steps are involved: Step 1: Based on the mass fraction of the reaction solution, 40-60 parts of silver nitrate are dissolved in 180-220 parts of water, and 40-60 parts of 25% (w / w) ammonia water are added to prepare a reaction solution; Step 2: Based on the mass fraction of the reducing solution, 3-4 parts of glucose, 3-5 parts of hydroxylamine hydrochloride and 7-8 parts of triethanolamine are dissolved in 180-220 parts of water, and 5-10 parts of sodium hydroxide are added to adjust the pH value to prepare a reducing solution; Step 3: respectively adjust the temperature of the reducing solution and the reaction solution to 30-40°C, and then add the reducing solution completely to the reaction solution within 1-10 minutes under stirring at 50-150 rpm to carry out a reduction reaction; Step 4: After the reducing solution is added, sodium polymethacrylate and N,N-dimethyl stearamide are added, and the mixture is stirred evenly to obtain a dispersion, wherein the mass ratio of the silver nitrate, sodium polymethacrylate and N,N-dimethyl stearamide is 100: (0.31-0.64): (0.19-0.5); Step 5: Filter, wash and dry the dispersion, wash it twice with banana water, and dry it to obtain micron-sized silver powder; The mass ratio of the reducing liquid to the reaction liquid in step 3 is 1:(1-1.5).

2. The method for preparing micron-sized silver powder according to claim 1, characterized in that: In the step 2, sodium hydroxide is added to adjust the pH value to within the range of 13-14. After the sodium hydroxide is added, stirring is performed at 50-150 rpm for 15-30 minutes to obtain a reducing solution.

3. The method for preparing micron-sized silver powder according to claim 1, characterized in that: In the step 4, continuing to stir evenly means stirring at a temperature of 30-40° C. and at a speed of 50-150 rpm for 30-40 min.

4. The method for preparing micron-sized silver powder according to claim 1, characterized in that: The median particle size of the micron-sized silver powder is below 3.0 μm.

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