High-filling and high-thermal-conductivity thick silver powder for slurry and preparation method of thick silver powder

Abstract

The invention discloses thick silver powder for high-filling and high-thermal-conductivity slurry and a preparation method of the thick silver powder, and belongs to the technical field of metal powder material processing, and the preparation method comprises the following steps: (1) selecting prepared monodisperse micron silver as a raw material; (2) carrying out emulsification treatment on the prepared monodisperse micron silver powder in the step (1) in a dispersion machine; (3) the monodisperse micron silver powder emulsified in the step (2) is put into a filter press for solid-liquid separation; (4) the monodisperse micron silver powder obtained after solid-liquid separation in the step (3) is put into a freeze dryer to be freeze-dried; (5) the freeze-dried monodisperse micron silver powder in the step (4) is sieved and put into a ball mill for ball milling; and (6) carrying out ball milling for 4 hours, detecting the particle size D501.8-2.2 mu m, discharging, sieving, cleaning, separating, freeze-drying and sieving to obtain a finished product. The flake silver powder prepared through the method is good in dispersity, thick in flake, good in thermal conductivity, resistant to a high-temperature environment and capable of being used for high-filling and high-thermal-conductivity slurry.

Description

Technical Field

[0001] This invention belongs to the field of metal powder material processing technology, specifically relating to the processing technology of electronic material functional powders, precious metal powders, and non-ferrous metal materials. It relates to a thick sheet silver powder for high-filling, high-thermal-conductivity slurry and its preparation method. Background Technology

[0002] Currently, the main methods for preparing flake silver powder are chemical and physical methods. Chemical methods are further divided into chemical reduction and electrolysis. Chemical reduction involves controlling grain growth through chemical reactions in an aqueous or organic phase to directly generate flake silver powder. The resulting flake silver powder is typically short, radially growing flakes on the surface of a single silver grain, resulting in poor compaction and insufficient filling rate in slurries. Electrolysis uses silver as the anode, passing electricity through an electrolyte solution, causing silver ions to deposit as flakes at the cathode. This type of silver powder has large particles and is suitable for high-purity smelting, but cannot be used in slurries.

[0003] Physical methods are divided into ball milling and vapor deposition. Ball milling involves putting silver powder and a dispersant into a ball mill, where the silver powder is crushed by the impact of the milling media into single-particle thick flakes. After drying and sieving, it has high filling capacity and thermal conductivity in slurry. Vapor deposition involves vaporizing elemental silver at high temperature and depositing it into a sheet film on a low-temperature substrate. The film is then peeled off and crushed. It has high purity but high cost.

[0004] There are existing studies on methods for preparing flake silver powder. For example, CN202410373020.7 discloses a method for preparing low-bulk flake silver powder and its application. The method involves mixing and dispersing wet silver powder, a dispersant, and a grinding aid to obtain a precursor slurry; subjecting the precursor slurry to a first-stage ball milling, followed by soaking, and a second-stage ball milling to obtain a flake silver slurry; washing the flake silver slurry, allowing it to stand, collecting the precipitate, and drying it to obtain low-bulk flake silver powder with a particle size D. 50 It is greater than 5μm.

[0005] CN202311557114.1 discloses a high-tap-density, lamellar, overlapping silver powder and its preparation method. The method involves preparing a 0.50M–2.0M sulfate solution and a 1.5M–3.0M silver nitrate solution. A first organic acid, a second organic acid, and 35%–45% (by volume) of the sulfate solution are added to a reaction vessel, and stirring is started. The temperature is controlled at 5℃–30℃. While stirring, the silver nitrate solution and 55%–65% (by volume) of the sulfate solution are simultaneously added dropwise to the reaction vessel, and stirring continues for 10–15 minutes. The mixture is then separated, washed, and dried to obtain high-tap-density, lamellar, overlapping silver powder with an average particle size of 3.5 μm or larger.

[0006] CN202410384841.0 discloses a method for preparing flake-shaped silver powder using a liquid-phase reaction method, belonging to the field of metal powder materials technology. This invention provides a method for preparing flake-shaped silver powder using a liquid-phase reaction method. The method includes the following steps: S1, mixing a dispersant, silver salt, water, template agent, and reducing agent solution and reacting them to obtain a seed solution; S2, mixing the dispersant, silver salt, water, template agent, and seed solution to obtain a mixed solution B; S3, mixing at least two reducing agents and water to obtain a mixed solution C; S4, mixing mixed solution B and mixed solution C and performing a redox reaction to obtain flake-shaped silver powder; steps S2 and S3 are not sequential. This method is simple to operate, requires mild reaction conditions, and yields flake-shaped silver powder particles with good dispersibility, meeting the requirements for low-cost preparation of high-quality silver powder.

[0007] Currently, commercially available flake silver powder is generally used in low-temperature thin-film pastes. These flakes are typically very thin, loosely packed, and have low tapping. When used in ordinary keyboard pastes, they can achieve low-temperature conductivity because the carrier shrinks, causing the flakes to shrink together and overlap to achieve low-temperature conductivity. In contrast, thick flake silver powder is loosely packed, has high tapping, is heat resistant, and has good flowability. It can achieve high filling and high thermal conductivity in pastes. This type of silver powder for pastes is currently mainly imported.

[0008] Therefore, the preparation of a thick sheet silver powder for a high-filling, high-thermal-conductivity paste has a promising market prospect. Summary of the Invention

[0009] To address the issue that commercially available flake silver powder is rarely used in the preparation of high-filler, high-thermal-conductivity pastes, there is an urgent need for a silver powder that is loosely packed, highly compacted, and thick. This invention provides a thick flake silver powder for high-filler, high-thermal-conductivity pastes and its preparation method. The flake silver powder prepared by this method has good dispersibility, thick flakes, good thermal conductivity, and high-temperature resistance, and can be used in high-filler, high-thermal-conductivity pastes.

[0010] The technical solution of the present invention is as follows: A method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity pastes includes the following steps: (1) Prepared monodisperse micron-sized silver was selected as the raw material; (2) The monodisperse micron silver powder prepared in step (1) is emulsified in a disperser; (3) The monodisperse micron silver powder emulsified in step (2) is placed into a filter press for solid-liquid separation; (4) Place the monodisperse micron silver powder that has been separated into solid and liquid in step (3) into a freeze dryer for freeze drying; (5) The freeze-dried monodisperse micron silver powder from step (4) is sieved and then ball-milled in a ball mill; (6) Particle size D was measured after ball milling for 4 hours. 50The material is discharged at a size of 1.8μm-2.2μm, then washed, filtered, pressure filtered, freeze-dried, and sieved to obtain the finished product.

[0011] The objective of this invention is achieved through the following technical solution: A method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity pastes includes the following steps: S1. Mix monodisperse micron silver powder and alcohol solvent and then emulsify them according to the ratio of 1 kg of monodisperse micron silver powder to (2-3) L of alcohol solvent. The monodisperse micron-sized silver powder has a particle size D 50 1.3μm-1.5μm, specific surface area 0.2m² 2 / g-0.4m 2 / g; S2. Dissolve the fatty acid in an alcohol solvent until it is completely dissolved to obtain solution A; The fatty acid is 0.4%-0.6% of the mass of the monodisperse micron silver powder, and the amount of alcohol solvent is based on a ratio of 1 kg of monodisperse micron silver powder to (4-5) L of alcohol solvent. S3. Add all of solution A to the emulsified material after S1, and stir thoroughly to obtain a uniformly emulsified monodisperse micron silver powder. S4. Filter the emulsified monodisperse micron silver powder by pressure. S5. Place the filtered monodisperse micron silver powder into a freeze dryer and dry it. S6. Pass the freeze-dried monodisperse micron silver powder through a 100-mesh sieve and directly feed it into a ball mill for mechanical ball milling; S7, ball mill to the test particle size D 50 The silver powder was ball-milled to a thickness of 1.8μm-2.2μm, then washed, filtered, pressure-filtered, freeze-dried, and passed through a 350-mesh sieve to obtain high-compact flake silver powder. This is also a thick flake silver powder for high-filling, high-thermal-conductivity slurries. The loose packing density of the silver powder is 3.20 g / cm³. 3 -3.6 g / cm 3 The tap density is 5.40 g / cm³. 3 -5.70 g / cm 3 Particle size is D 50 1.8μm-2.2μm, specific surface area is 0.5 m² 2 / g-0.6 m 2 / g.

[0012] Furthermore, the alcohol solvent mentioned in S1 is selected from one of glycerol, diethylene glycol, anhydrous ethanol, ethylene glycol, and isopropanol.

[0013] The emulsification process is carried out in a disperser for 20-30 minutes.

[0014] Furthermore, S1 is prepared according to a ratio of 1 kg of monodisperse micron-sized silver powder to 2 L of alcohol solvent.

[0015] Furthermore, the fatty acid described in S2 is selected from one of palmitic acid, oleic acid, glyceryl oleate, stearic acid, glyceryl stearate, and cetyl alcohol.

[0016] Furthermore, in S3, the mixture is stirred thoroughly for 10-30 minutes.

[0017] Furthermore, in S4, the emulsified monodisperse micron silver powder is placed into a filter press for filtration, wherein the filter air is free of moisture and the air pressure is ≤0.5MPa.

[0018] Furthermore, the freezing temperature in S5 is -80°C, and the drying temperature is 35°C.

[0019] Furthermore, in the mechanical ball milling described in S6, the mechanical ball milling solvent is selected from one of glycerol, diethylene glycol, anhydrous ethanol, ethylene glycol, and isopropanol.

[0020] Furthermore, the cleaning, filtration, pressure filtration, and freeze drying described in S7 specifically involve taking out the spherical powder together, adding anhydrous ethanol, cleaning and filtering with a 300-mesh sieve, placing the filtered thick flake silver powder into a filter press, adjusting the pressure to 0.4 MPa and pressing until no liquid flows out from the bottom of the filter tank, then adding anhydrous ethanol and pressing again. After pressing, stop pressing, remove the filtered thick flake silver, and freeze-dry it in a freeze dryer at -80℃ for 24 hours.

[0021] This invention also relates to a thick sheet silver powder for high-filler, high-thermal-conductivity pastes, obtained by the aforementioned method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity pastes, wherein the loose bulk density of the silver powder is 3.20 g / cm³. 3 -3.6 g / cm 3 The tap density is 5.40 g / cm³. 3 -5.70 g / cm 3 Particle size is D 50 1.8μm-2.2μm, specific surface area is 0.5 m² 2 / g-0.6 m 2 / g.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. The thick sheet silver powder for high-filler, high-thermal-conductivity slurry described in this invention has good dispersibility, thick sheet shape, good thermal conductivity, and high-temperature resistance, and can be used in high-filler, high-thermal-conductivity slurries.

[0023] 2. The method for preparing thick flake silver powder for high-filler, high-thermal-conductivity slurries according to the present invention first emulsifies monodisperse micron-sized silver powder, coating the surface of the monodisperse micron-sized silver powder with fatty acids. The monodisperse micron-sized silver powder is then freeze-dried at low temperature and sieved without altering the particle properties. Next, it is ball-milled in a ball mill to produce thick flake silver powder meeting the requirements. Finally, it is obtained by pressure filtration, low-temperature freeze-drying, and sieving to obtain the monodisperse thick flake silver powder. Compared with existing methods, the advantages of the preparation method of the present invention are that the flake silver powder prepared by this method has good dispersibility, thick flakes, good thermal conductivity, and resistance to high-temperature environments, and can be used in high-filler, high-thermal-conductivity slurries. Attached Figure Description

[0024] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0025] Figure 1 This is a 10,000x partial scanning electron microscope image of silver powder prepared by a method for preparing thick sheet silver powder for high-filling, high-thermal-conductivity slurry according to Embodiment 1 of the present invention. Figure 2 This is a 20,000x partial scanning electron microscope image of silver powder prepared by a method for preparing thick sheet silver powder for high-filling, high-thermal-conductivity slurry according to Embodiment 1 of the present invention. Detailed Implementation

[0026] The preferred embodiments of the present invention will be described in further detail below, but the present invention is not limited to these embodiments.

[0027] Example 1: A method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity pastes includes the following steps: (1) Preparation of thick sheet silver powder: Add 4L of anhydrous ethanol and 2L of deionized water to the emulsification tank, and add 3kg of monodisperse micron silver powder under stirring to make it completely dispersed; then add oleic acid equivalent to 0.6% of the mass fraction of monodisperse micron silver powder to the emulsification tank and stir for 30min to obtain solution A; take out the emulsified solution A and add it to the filter press, adjust the pressure to 0.4MPa and filter until no liquid flows out from the bottom of the filter press, stop the filter press and take out the monodisperse micron silver powder after filtration, put it into the freeze dryer to freeze dry at -80℃, take it out after 24h and pass it through a 100-mesh sieve; (2) Ball milling treatment: 3 kg of sieved monodisperse micron silver powder was put into a ball mill, 3 L of ethylene glycol was added, the ball milling media was 0.5 mm zirconia balls, the ball mill frequency was adjusted to 40 Hz, the ball milling time was 4 h, and the particle size D was measured. 501.8-2.2μm, take out the spherical powder together, add anhydrous ethanol and wash and filter with a 300-mesh sieve. Put the filtered thick flake silver powder into a filter press and press it. Adjust the pressure to 0.4MPa and press until no liquid flows out from the bottom of the filter tank. Then add 3L of anhydrous ethanol and press it. After pressing, stop the pressing and take out the thick flake silver powder. Put it into a freeze dryer and freeze dry at -80℃. After 24 hours, take it out and pass it through a 350-mesh sieve to obtain high-compact flake silver powder. The technical specifications of the obtained silver powder are as follows: Loose bulk density of silver powder: 3.2 g / cm³ 3 Tap density 5.40 g / cm³ 3 Particle size D 50 1.94 μm, specific surface area 0.55 m² 2 / g.

[0028] Figure 1 This is a 20,000x partial scanning electron microscope image of the silver powder prepared in Example 1, showing that the particle size of the powder is within the D... 50 The thickness is between 1.8 and 2.2 μm, which is within the product design range; Figure 2 This is a 10,000x scanning electron microscope image of the silver powder prepared in Example 1. It can be seen that all the silver powder particles have been ball-milled into thick flakes, meeting the product design requirements.

[0029] Example 2: A method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity pastes includes the following steps: (1) Preparation of thick sheet silver powder: Add 4L of anhydrous ethanol and 2L of deionized water to the emulsification tank, and add 3kg of micron silver powder under stirring to make it completely dispersed; then dissolve stearic acid equivalent to 0.6% of the mass fraction of monodisperse micron silver powder in 50ml of hot anhydrous ethanol to form solution B. Add solution B to the emulsification tank and stir for 30min to obtain solution A; take out the emulsified solution A and add it to the filter press. Adjust the pressure to 0.4MPa and filter until no liquid flows out from the bottom of the filter press. Stop the filter press and take out the monodisperse micron silver powder after filter pressing. Put it into the freeze dryer for freeze drying at -80℃. After 24h, take it out and pass it through a 100-mesh sieve. (2) Ball milling treatment: 3 kg of sieved monodisperse micron silver powder was put into a ball mill, 3 L of ethylene glycol was added, the ball milling media was 0.5 mm zirconia balls, the ball mill frequency was adjusted to 40 Hz, the ball milling time was 4 h, and the particle size D was measured. 50Take out the 1.8-2.2μm ball powder together, add anhydrous ethanol and wash and filter with a 300-mesh sieve. Put the filtered thick flake silver powder into a filter press and press it. Adjust the pressure to 0.4MPa and press until no liquid flows out from the bottom of the filter press. Then add 3L of anhydrous ethanol and press it. After pressing, stop the pressing and take out the thick flake silver powder. Put it into a freeze dryer and freeze dry at -80℃ for 24 hours. Take it out and pass it through a 350-mesh sieve to obtain high-compact flake silver powder. The technical specifications of the obtained silver powder are as follows: Loose bulk density of silver powder: 3.3 g / cm³ 3 Tap density 5.60 g / cm³ 3 Particle size D 50 1.98μm, specific surface area 0.53 m² 2 / g.

[0030] Example 3: A method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity pastes includes the following steps: (1) Preparation of thick sheet silver powder: Add 3L of anhydrous ethanol and 1L of deionized water to the emulsification tank. Under stirring, add 3kg of monodisperse micron silver powder to disperse it completely. Then dissolve stearic acid equivalent to 0.6% of the mass fraction of monodisperse micron silver powder in 50ml of hot anhydrous ethanol to form solution B. Add solution B to the emulsification tank and stir for 30min to obtain solution A. Take out the emulsified solution A and add it to the filter press. Adjust the pressure to 0.4MPa and filter until no liquid flows out from the bottom of the filter tank. Stop the filter press and take out the micron silver powder after filtration. Put it into the freeze dryer for freeze drying at -80℃. After 24h, take it out and pass it through a 100-mesh sieve. (2) Ball milling treatment: 3 kg of sieved monodisperse micron silver powder was placed into a ball mill, 2 L of ethylene glycol and 1 L of anhydrous ethanol were added, the ball milling media was 0.5 mm zirconia balls, the ball mill frequency was adjusted to 40 Hz, the ball milling time was 4 h, and the particle size D was measured. 50 1.8-2.2μm, take out the spherical powder together, add anhydrous ethanol and wash and filter with a 300-mesh sieve. Put the filtered thick flake silver powder into a filter press and press it. Adjust the pressure to 0.4MPa and press until no liquid flows out from the bottom of the filter tank. Then add 3L of anhydrous ethanol and press it. After pressing, stop the pressing and take out the thick flake silver powder. Put it into a freeze dryer and freeze dry at -80℃. After 24 hours, take it out and pass it through a 350-mesh sieve to obtain high-compact flake silver powder. The technical specifications of the obtained silver powder are as follows: Loose bulk density of silver powder: 3.2 g / cm³ 3 Tap density 5.4 g / cm³ 3 Particle size D 50 1.86 μm, specific surface area 0.55 m² 2 / g.

[0031] Example 4: A method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity pastes includes the following steps: (1) Preparation of thick sheet silver powder: Add 3L of anhydrous ethanol and 1L of deionized water to the emulsification tank, and add 3kg of monodisperse micron silver powder under stirring to make it completely dispersed; then dissolve 0.25% oleic acid + 0.25% stearic acid equivalent to the mass fraction of monodisperse micron silver powder in 50ml of hot anhydrous ethanol to form solution B. Add solution B to the emulsification tank and stir for 30min to obtain solution A; take out the emulsified solution A and add it to the filter press. Adjust the pressure to 0.4MPa and filter until no liquid flows out from the bottom of the filter tank. Stop the filter press and take out the micron silver powder after filtration. Put it into the freeze dryer for freeze drying at -80℃. After 24h, take it out and pass it through a 100-mesh sieve. (2) Ball milling treatment: 3 kg of sieved monodisperse micron silver powder was placed into a ball mill, 1 L of ethylene glycol and 2 L of anhydrous ethanol were added, the ball milling media was 0.8 mm zirconia balls, the ball mill frequency was adjusted to 40 Hz, the ball milling time was 3 h, and the particle size D was measured. 50 1.8-2.2μm, take out the spherical powder together, add anhydrous ethanol and wash and filter with a 300-mesh sieve. Put the filtered thick flake silver powder into a filter press and press it. Adjust the pressure to 0.4MPa and press until no liquid flows out from the bottom of the filter tank. Then add 3L of anhydrous ethanol and press it. After pressing, stop the pressing and take out the thick flake silver powder. Put it into a freeze dryer and freeze dry at -80℃. After 24 hours, take it out and pass it through a 350-mesh sieve to obtain high-compact flake silver powder. The technical specifications of the obtained silver powder are as follows: Loose bulk density of silver powder: 3.5 g / cm³ 3 Tap density 5.6 g / cm³ 3 Particle size D 50 1.98 μm, specific surface area 0.56 m² 2 / g.

[0032] Example 5: A method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity pastes includes the following steps: (1) Preparation of thick sheet silver powder: Add 3L of anhydrous ethanol and 1L of deionized water to the emulsification tank, and add 3kg of micron silver powder under stirring to make it completely dispersed; then add 0.6% oleic acid of micron silver mass fraction to the emulsification tank and stir for 30min to obtain solution A; take out the emulsified solution A and add it to the filter press, adjust the pressure to 0.4MPa and filter until no liquid flows out from the bottom of the filter press, stop the filter press and take out the micron silver after filter pressing, put it into the freeze dryer to freeze dry at -80℃, take it out after 24h and pass it through a 100 mesh sieve; (2) Ball milling treatment: 3 kg of sieved silver powder was put into a ball mill, 2 L of ethylene glycol and 1 L of anhydrous ethanol were added, the ball milling media was 0.8 mm zirconia balls, the ball mill frequency was adjusted to 40 Hz, the ball milling time was 3 h, and the particle size D was measured. 50 1.8-2.2μm, take out the spherical powder together, add anhydrous ethanol and wash and filter with a 300-mesh sieve. Put the filtered thick flake silver powder into a filter press and press it. Adjust the pressure to 0.4MPa and press until no liquid flows out from the bottom of the filter tank. Then add 3L of anhydrous ethanol and press it. After pressing, stop the pressing and take out the thick flake silver powder. Put it into a freeze dryer and freeze dry at -80℃. After 24 hours, take it out and pass it through a 350-mesh sieve to obtain high-compact flake silver powder. The technical specifications of the obtained silver powder are as follows: Loose bulk density of silver powder: 3.56 g / cm³ 3 Tap density 5.70 g / cm³ 3 Particle size D 50 2.10 μm, specific surface area 0.58 m² 2 / g.

[0033] Comparative Example 1: Compared with Example 1, the difference is that in Comparative Example 1, wet silver powder was ball-milled in two stages to obtain low-bulk, large-flake silver powder D. 50 >5μm; In Example 1, monodisperse micron-sized silver powder was first emulsified, freeze-dried, and then ball-milled to obtain D. 50 <2.20μm high-impact thick sheet silver powder.

[0034] Comparative Example 2: Compared to Example 1, the difference lies in that Comparative Example 2 is a sheet-like overlapping silver powder prepared by chemically reacting two organic acids with a sulfate solution, with an average particle size D. 50 3.5μm; In Example 1, monodisperse micron-sized silver powder was first emulsified, freeze-dried, and then ball-milled to obtain D. 50 <2.20μm monodisperse thick flake silver powder.

[0035] Results analysis: 1. As can be seen from Examples 1-5, the thick sheet silver powder obtained by the preparation method of the high-filling, high-thermal-conductivity paste of the present invention can be used simultaneously in low-temperature conductive silver paste and low-temperature sintering silver paste. The loose packing density of the silver powder is 3.20 g / cm³. 3 -3.6 g / cm 3 The tap density is 5.40 g / cm³. 3 -5.70 g / cm 3 Particle size is D 50 1.8μm-2.2μm, specific surface area is 0.5 m²2 / g-0.6 m 2 / g.

[0036] 2. By comparing Example 1 with Comparative Example 1, it can be seen that different ball milling methods for silver powder of different particle sizes can lead to coarser initial products, resulting in the final ball milled products exceeding the reasonable particle size range. Large flakes and low packing size can prevent high filling in subsequent pulping.

[0037] 3. By comparing Example 1 and Comparative Example 2, it can be illustrated that the flake-like overlapping silver powder prepared by chemically reacting two organic acids with a sulfate solution has an average particle size D. 50 The 3.5μm size distribution of the final reaction product is uneven and the silver flakes overlap, resulting in poor silver powder dispersion. Furthermore, the resistivity increases and the printing performance is poor after the paste is prepared.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity pastes, characterized in that, Includes the following steps: S1. Mix monodisperse micron silver powder and alcohol solvent and then emulsify them according to the ratio of 1 kg of monodisperse micron silver powder to (2-3) L of alcohol solvent. The monodisperse micron-sized silver powder has a particle size D 50 1.3μm-1.5μm, specific surface area 0.2m² 2 / g-0.4m 2 / g; S2. Dissolve the fatty acid in an alcohol solvent until it is completely dissolved to obtain solution A; The fatty acid is 0.4%-0.6% of the mass of the monodisperse micron silver powder, and the amount of alcohol solvent is based on a ratio of 1 kg of monodisperse micron silver powder to (4-5) L of alcohol solvent. S3. Add all of solution A to the emulsified material after S1, and stir thoroughly to obtain a uniformly emulsified monodisperse micron silver powder. S4. Filter the emulsified monodisperse micron silver powder by pressure. S5. Place the filtered monodisperse micron silver powder into a freeze dryer and dry it. S6. Pass the freeze-dried monodisperse micron silver powder through a 100-mesh sieve and directly feed it into a ball mill for mechanical ball milling; S7, ball mill to the test particle size D 50 The silver powder was ball-milled to a thickness of 1.8μm-2.2μm, then washed, filtered, pressure-filtered, freeze-dried, and passed through a 350-mesh sieve to obtain high-compact flake silver powder. This is also a thick flake silver powder for high-filling, high-thermal-conductivity slurries. The loose packing density of the silver powder is 3.20 g / cm³. 3 -3.6 g / cm 3 The tap density is 5.40 g / cm³. 3 -5.70 g / cm 3 Particle size is D 50 1.8μm-2.2μm, specific surface area is 0.5 m² 2 / g-0.6 m 2 / g.

2. The method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity paste according to claim 1, characterized in that, The alcohol solvent mentioned in S1 is selected from one of glycerol, diethylene glycol, anhydrous ethanol, ethylene glycol, and isopropanol.

3. The method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity paste according to claim 1, characterized in that, The emulsification process described in S1 is carried out in a disperser for 20-30 minutes.

4. The method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity paste according to claim 1, characterized in that, S1 is prepared according to the ratio of 1 kg of monodisperse micron silver powder to 2 L of alcohol solvent.

5. The method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity paste according to claim 1, characterized in that, The fatty acid described in S2 is selected from one of palmitic acid, oleic acid, glyceryl oleate, stearic acid, glyceryl stearate, and cetyl alcohol.

6. The method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity paste according to claim 1, characterized in that, In S3, stir thoroughly for 10-30 minutes.

7. The method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity paste according to claim 1, characterized in that, In S4, the emulsified monodisperse micron silver powder is placed into a filter press for filtration. The filter air is free of moisture and the air pressure is ≤0.5MPa.

8. The method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity paste according to claim 1, characterized in that, The freezing temperature in S5 is -80℃, and the drying temperature is 35℃.

9. The method for preparing thick sheet silver powder for high-filler, high-thermal-conductivity paste according to claim 1, characterized in that, The mechanical ball milling solvent described in S6 is selected from one of glycerol, diethylene glycol, anhydrous ethanol, ethylene glycol, and isopropanol.

10. A thick sheet silver powder for a high-filler, high-thermal-conductivity paste, characterized in that, The silver powder is obtained by a method for preparing thick sheet silver powder for high-filling, high-thermal-conductivity paste according to any one of claims 1-9, wherein the loose bulk density of the silver powder is 3.20 g / cm³. 3 -3.6 g / cm 3 The tap density is 5.40 g / cm³. 3 -5.70 g / cm 3 Particle size is D 50 1.8μm-2.1μm, specific surface area is 0.5 m² 2 / g-0.6 m 2 / g.

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