Preparation method of high specific surface area silver particles for low temperature sintering silver paste

Abstract

The application provides a preparation method of high specific surface area silver particles for low-temperature sintering silver paste, and belongs to the technical field of conductive materials, and comprises the following steps: ammonia is added into a hydrazine hydrate solution with a molar concentration of 1.60-6.0 mol / L until the pH of the hydrazine hydrate solution is 10-13; an alpha-amino acid aqueous solution with a molar concentration of 0.012-0.048 mol / L is prepared at a temperature of 35-45 DEG C; the hydrazine hydrate solution and a silver nitrate solution are simultaneously added into the alpha-amino acid solution within 8-12 min, and then stirring, heating, adding a sodium hydroxide solution to adjust the pH of the reaction solution to 11-13, and continuously stirring are carried out; and finally, aging, separation, washing and drying are carried out to obtain the high specific surface area silver particles. The application can realize the controllability of the particle size and the specific surface area of the silver particles under the premise of ensuring the conductive performance of the high specific surface area silver particles, meets the stability requirement of the silver powder as a conductive filler, and has a high yield.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of conductive materials, and particularly relates to a preparation method of high specific surface area silver microparticles for low-temperature sintering silver paste. BACKGROUND

[0002] Low-temperature sintering silver paste is widely used in fields such as printed circuit boards, touch screens and automobile electronics. Compared with traditional conductive materials, low-temperature sintering silver paste can exhibit high conductivity and excellent mechanical properties at a lower sintering temperature, and low-temperature sintering can avoid damage to the substrate material. Therefore, low-temperature sintering silver paste technology will become one of the important development trends in the field of conductive materials. However, in practical applications, low-temperature sintering silver paste is inevitably shackled by the preparation technology of conductive fillers. There are two common conductive fillers for low-temperature sintering silver paste, one is flaky silver powder, and the other is nano silver powder. The flaky silver powder is mainly prepared by a two-step method of chemical reduction-mechanical ball milling, and the long production process not only reduces the production efficiency, but also has a relatively low recovery rate of flaky silver powder, and the flaky silver powder has a high processing cost. The nano silver powder is prepared by a one-step chemical reduction method. Since the nano silver powder has high dispersibility and small average particle size, existing solid-liquid separation technologies cannot meet market demand. SUMMARY

[0003] The purpose of the present application is to provide a preparation method of high specific surface area silver microparticles for low-temperature sintering silver paste, which can realize the controllability of the particle size and specific surface area of the silver microparticles while ensuring the conductivity of the high specific surface area silver microparticles, meet the stability requirements of silver powder as a conductive filler, and has a high yield.

[0004] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0005] A preparation method of high specific surface area silver microparticles for low-temperature sintering silver paste, the preparation method comprising the following steps:

[0006] Step S1, ammonia is added to a hydrazine hydrate solution with a molar concentration of 1.60-6.0 mol / L until the pH of the hydrazine hydrate solution is 10-13;

[0007] Step S2, an alpha-amino acid aqueous solution with a molar concentration of 0.012-0.048 mol / L is prepared at a temperature of 35-45℃;

[0008] Step S3, the hydrazine hydrate solution with pH of 10-13 and the silver nitrate solution with molar concentration of 0.60-2.4 mol / L are simultaneously added into the α-amino acid solution within 8-12 min, stirring for 2-7 min, then heating to 75-85℃, adding the sodium hydroxide solution to adjust the pH of the reaction solution to 11-13, continuing to stir for 2-7 min, aging for 25-35 min, and finally separating, washing and drying to obtain the silver microparticles with high specific surface area;

[0009] In the step S3, the mass ratio of the hydrazine hydrate in the hydrazine hydrate solution, the silver nitrate in the silver nitrate solution and the α-amino acid in the α-amino acid solution is 10-100:1:50-200.

[0010] Further, in the step S1, the mass concentration of the ammonia water is 25-28%.

[0011] Further, in the step S2, the α-amino acid is one of glycine, histidine, tryptophan and arginine.

[0012] Further, in the step S3, the mass ratio of the hydrazine hydrate in the hydrazine hydrate solution, the silver nitrate in the silver nitrate solution and the α-amino acid in the α-amino acid solution is 30-70:1:80-170.

[0013] Further, in the step S3, the mass ratio of the hydrazine hydrate in the hydrazine hydrate solution, the silver nitrate in the silver nitrate solution and the α-amino acid in the α-amino acid solution is 45-65:1:115-145.

[0014] Further, in the step S3, the drying temperature is 95-105℃, and the time is 11-13 h.

[0015] Further, in the step S3, the D50 of the silver microparticles with high specific surface area is 8.66-11.4 μm, the D100 is 14.7-15.7 μm, and the specific surface area is 12-17.8 m 2 / g.

[0016] In summary, the scheme provided by the present application has the following technical effects:

[0017] The strong reducing capacity of the hydrazine hydrate solution enables silver ions in the silver nitrate solution to be completely converted into silver microparticles, and the yield of the silver microparticles is improved; the small molecule alpha-amino acid complexing agent improves the specific surface area of the silver microparticles, and does not reduce the low-temperature slurry electrical performance, thereby meeting the stability requirement of silver powder as a conductive filler, and the yield is high; the temperature of the oxidation-reduction reaction is controlled, and the agglomeration of free nanoparticles is promoted, and free nanoparticles are not observed in the electron microscope photos, the specific surface area is indirectly controlled to control the particle size of the silver particles, and the maximum particle size is controllable. DETAILED DESCRIPTION

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below clearly and completely. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0019] Embodiment 1

[0020] 1. Ammonia water with a mass concentration of 25% is added to a hydrazine hydrate solution with a molar concentration of 2.0 mol / L until the pH value of the hydrazine hydrate solution is 11.

[0021] 2. An alpha-amino acid aqueous solution with a molar concentration of 0.030 mol / L is configured at a temperature of 40℃.

[0022] 3. The hydrazine hydrate solution with a pH of 11 and the silver nitrate solution with a molar concentration of 1.0 mol / L are simultaneously added to the alpha-amino acid solution within 10 min by using a peristaltic pump in a bidirectional adding mode, after the addition is completed, stirring is performed for 5 min, then the temperature is raised to 80℃, a sodium hydroxide solution is added to adjust the pH of the reaction solution to 12, then stirring is continued for 5 min, and then aging is performed for 30 min, and then separation and washing are performed, and drying is performed at 100℃ for 12 h to obtain high specific surface area silver microparticles.

[0023] The mass ratio of hydrazine hydrate in the hydrazine hydrate solution, silver nitrate in the silver nitrate solution, and alpha-amino acid in the alpha-amino acid solution is 65:1:145.

[0024] The D50 of the high specific surface area silver microparticles in this embodiment is 9.2 μm, the D100 is 15.1 μm, the specific surface area measured by a dynamic nitrogen adsorption specific surface area instrument is 12 m 2 / g, and the direct yield of silver powder is 99.7%.

[0025] Embodiment 2

[0026] 1. Add ammonia water with a mass concentration of 28% to hydrazine hydrate solution with a molar concentration of 4.0 mol / L until the pH of the hydrazine hydrate solution is 13.

[0027] 2. Prepare an α-amino acid aqueous solution with a molar concentration of 0.048 mol / L at a temperature of 35°C.

[0028] 3. Using a peristaltic pump, simultaneously add the hydrazine hydrate solution with a pH of 13 and the silver nitrate solution with a molar concentration of 1.6 mol / L to the α-amino acid solution within 12 min, after the addition is complete, stir for 7 min, then raise the temperature to 85°C, add sodium hydroxide solution to adjust the pH of the reaction solution to 13, continue stirring for 7 min, then age for 35 min, then separate and wash, and dry at 105°C for 13 h to obtain high specific surface area silver particles.

[0029] The mass ratio of hydrazine hydrate in the hydrazine hydrate solution, silver nitrate in the silver nitrate solution, and α-amino acid in the α-amino acid solution is 70:1:170.

[0030] The D50 of the high specific surface area silver particles of the present embodiment is 11.4 μm, the D100 is 15.7 μm, the specific surface area is 14.2 m 2 / g as measured by a dynamic nitrogen adsorption specific surface area instrument, and the silver powder yield is 99.9%.

[0031] Example 3:

[0032] 1. Add ammonia water with a mass concentration of 28% to hydrazine hydrate solution with a molar concentration of 1.6 mol / L until the pH of the hydrazine hydrate solution is 10.

[0033] 2. Prepare an α-amino acid aqueous solution with a molar concentration of 0.012 mol / L at a temperature of 45°C.

[0034] 3. Using a peristaltic pump, simultaneously add the hydrazine hydrate solution with a pH of 10 and the silver nitrate solution with a molar concentration of 0.6 mol / L to the α-amino acid solution within 8 min, after the addition is complete, stir for 3 min, then raise the temperature to 75°C, add sodium hydroxide solution to adjust the pH of the reaction solution to 11, continue stirring for 3 min, then age for 25 min, then separate and wash, and dry at 95°C for 11 h to obtain high specific surface area silver particles.

[0035] The mass ratio of hydrazine hydrate in the hydrazine hydrate solution, silver nitrate in the silver nitrate solution, and α-amino acid in the α-amino acid solution is 10:1:50.

[0036] The D50 of the high specific surface area silver particles of this example is 9.13 μm, the D100 is 14.7 μm, the specific surface area is 15.4 m2 / g, and the direct silver powder yield is 99.6% as measured by a laser particle size distribution instrument. 2 / g, and the direct silver powder yield is 99.6%.

[0037] Example 4:

[0038] 1. Ammonia water with a mass concentration of 26% is added to a hydrazine hydrate solution with a molar concentration of 6.0 mol / L until the pH of the hydrazine hydrate solution is 12.

[0039] 2. An α-amino acid aqueous solution with a molar concentration of 0.024 mol / L is prepared at a temperature of 38°C.

[0040] 3. The hydrazine hydrate solution with a pH of 12 and the silver nitrate solution with a molar concentration of 2.4 mol / L are simultaneously added to the α-amino acid solution within 10 min using a peristaltic pump in a bidirectional manner. After the addition is completed, the solution is stirred for 2 min, then the temperature is raised to 75°C, and a sodium hydroxide solution is added to adjust the pH of the reaction solution to 12. After stirring for another 2 min, the solution is aged for 30 min, then separated and washed, and dried at 100°C for 11 h to obtain high specific surface area silver particles.

[0041] The mass ratio of hydrazine hydrate in the hydrazine hydrate solution, silver nitrate in the silver nitrate solution, and α-amino acid in the α-amino acid solution is 30:1:80.

[0042] The D50 of the high specific surface area silver particles of this example is 8.66 μm, the D100 is 15.6 μm, the specific surface area is 17.8 m2 / g, and the direct silver powder yield is 99.7% as measured by a laser particle size distribution instrument. 2 / g, and the direct silver powder yield is 99.6%.

[0043] Note that the technical features of the above examples can be combined in any manner. In order to make the description simple, all possible combinations of the technical features in the above examples are not described, however, as long as the combinations of the technical features do not contradict each other, they should be considered as within the scope of the present disclosure. The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be construed as limiting the scope of the patent. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing high specific surface area silver microparticles for low-temperature sintering silver paste, characterized in that, The preparation method includes the following steps: Step S1: Add ammonia water to a hydrazine hydrate solution with a molar concentration of 1.60–6.0 mol / L until the pH of the hydrazine hydrate solution is 10–13; Step S2: Prepare an α-amino acid aqueous solution with a molar concentration of 0.012–0.048 mol / L at a temperature of 35℃–45℃; Step S3: A hydrazine hydrate solution with a pH of 10–13 and a silver nitrate solution with a molar concentration of 0.60–2.4 mol / L are simultaneously added dropwise to an α-amino acid solution over 8–12 minutes. After stirring for 2–7 minutes, the temperature is raised to 75–85°C. Sodium hydroxide solution is then added to adjust the pH of the reaction solution to 11–13. Stirring continues for 2–7 minutes, followed by aging for 25–35 minutes. Finally, the solution is separated, washed, and dried to obtain silver microparticles with high specific surface area. In step S3, the mass ratio of hydrazine hydrate in the hydrazine hydrate solution, silver nitrate in the silver nitrate solution, and α-amino acid in the α-amino acid solution is 10-100:1:50-200. In step S3, the high specific surface area silver microparticles have a D50 of 8.66–11.4 μm, a D100 of 14.7–15.7 μm, and a specific surface area of ​​12–17.8 μm. 2 / g.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass concentration of the ammonia water is 25-28%.

3. The preparation method according to claim 2, characterized in that, In step S2, the α-amino acid is one of glycine, histidine, tryptophan, and arginine.

4. The preparation method according to claim 3, characterized in that, In step S3, the mass ratio of hydrazine hydrate in the hydrazine hydrate solution, silver nitrate in the silver nitrate solution, and α-amino acid in the α-amino acid solution is 30-70:1:80-170.

5. The preparation method according to claim 4, characterized in that, In step S3, the mass ratio of hydrazine hydrate in the hydrazine hydrate solution, silver nitrate in the silver nitrate solution, and α-amino acid in the α-amino acid solution is 45-65:1:115-145.

6. The preparation method according to claim 5, characterized in that, In step S3, the drying temperature is 95-105°C and the drying time is 11-13 hours.