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

Abstract

The invention provides a preparation method of high-specific-surface-area silver particles for low-temperature sintered silver paste, and belongs to the technical field of conductive materials, and the preparation method comprises the following steps: adding ammonia water into a hydrazine hydrate solution with the molar concentration of 1.60-6.0 mol / L until the pH value of the hydrazine hydrate solution is 10-13; the method comprises the following steps: preparing an alpha-amino acid aqueous solution with the molar concentration of 0.012-0.048 mol / L at the temperature of 35-45 DEG C; the preparation method comprises the following steps: dropwise adding a hydrazine hydrate solution and a silver nitrate solution into an alpha-amino acid solution at the same time within 8-12min, stirring, heating, adding a sodium hydroxide solution to adjust the pH value of a reaction solution to 11-13, continuously stirring, aging, separating, washing and drying to obtain the silver particles with high specific surface area. On the premise of ensuring the conductivity of the high-specific-surface-area silver particles, the particle size and the specific surface area of the silver particles are controllable, the requirement for the stability of the silver powder serving as the conductive filler is met, and the yield is high.

Description

Technical Field

[0001] The invention belongs to the technical field of conductive materials, and in particular relates to a method for preparing silver particles with high specific surface area for low-temperature sintering silver paste. Background Art

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

[0003] The purpose of the present invention is to provide a method for preparing high specific surface area silver particles for low temperature sintering silver paste. The method can achieve controllable particle size and specific surface area of ​​the silver particles while ensuring the conductive properties of the high specific surface area silver particles, meet the stability requirements of silver powder as a conductive filler, and have a high yield.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

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

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

[0007] Step S2, preparing an α-amino acid aqueous solution with a molar concentration of 0.012 to 0.048 mol / L at a temperature of 35° C. to 45° C.;

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

[0009] In the 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.

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

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

[0012] Furthermore, 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.

[0013] Furthermore, 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.

[0014] Furthermore, in step S3, the drying temperature is 95-105° C. and the drying time is 11-13 hours.

[0015] Furthermore, in step S3, the high specific surface area silver particles have a D50 of 8.66 to 11.4 μm, a D100 of 14.7 to 15.7 μm, and a specific surface area of ​​12 to 17.8 m 2 / g.

[0016] In summary, the solution proposed by the present invention has the following technical effects:

[0017] The invention uses the strong reducing ability of the hydrazine hydrate solution to completely convert the silver ions in the silver nitrate solution into silver microparticles, thereby improving the yield of the silver microparticles; uses a small molecule α-amino acid complexing agent to improve the specific surface area of ​​the silver microparticles without reducing the electrical properties of the low-temperature slurry, thereby meeting the stability requirement of the silver powder as a conductive filler and having a high yield; and controls the temperature of the redox reaction to promote the agglomeration of free nanoparticles, wherein no free nanoparticles are observed to exist independently in an electron microscope photograph, and the particle size of the silver particles can be indirectly controlled by chemically regulating the specific surface area, and the maximum particle size is controllable. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Embodiment 1:

[0020] 1. Add 25% ammonia water to 2.0 mol / L hydrazine hydrate solution until the pH value of the hydrazine hydrate solution reaches 11.

[0021] 2. At a temperature of 40°C, prepare an α-amino acid aqueous solution with a molar concentration of 0.030 mol / L.

[0022] 3. Use a peristaltic pump in a bidirectional manner to simultaneously add a hydrazine hydrate solution with a pH of 11 and a silver nitrate solution with a molar concentration of 1.0 mol / L to the α-amino acid solution within 10 minutes. After the addition is completed, stir for 5 minutes, heat to 80°C, add sodium hydroxide solution to adjust the pH of the reaction solution to 12, continue stirring for 5 minutes, age for 30 minutes, separate and wash, and dry at 100°C for 12 hours to obtain high specific surface area silver particles.

[0023] 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 65:1:145.

[0024] The laser particle size distribution instrument measured the high specific surface area silver particles of this embodiment with a D50 of 9.2 μm and a D100 of 15.1 μm. The dynamic nitrogen adsorption specific surface area instrument measured the specific surface area of ​​12 m 2 / g, the direct recovery rate of silver powder is 99.7%.

[0025] Embodiment 2:

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

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

[0028] 3. Use a peristaltic pump in a bidirectional manner to simultaneously add a hydrazine hydrate solution with a pH of 13 and a silver nitrate solution with a molar concentration of 1.6 mol / L to the α-amino acid solution within 12 minutes. After the addition is completed, stir for 7 minutes, heat to 85°C, add sodium hydroxide solution to adjust the pH of the reaction solution to 13, continue stirring for 7 minutes, age for 35 minutes, separate and wash, and dry at 105°C for 13 hours 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 laser particle size distribution instrument measured the high specific surface area silver particles of this embodiment with a D50 of 11.4 μm and a D100 of 15.7 μm. The dynamic nitrogen adsorption specific surface area instrument measured the specific surface area of ​​14.2 m 2 / g, the direct recovery rate of silver powder is 99.9%.

[0031] Embodiment 3:

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

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

[0034] 3. Use a peristaltic pump in a bidirectional manner to simultaneously add a hydrazine hydrate solution with a pH of 10 and a silver nitrate solution with a molar concentration of 0.6 mol / L to the α-amino acid solution within 8 minutes. After the addition is completed, stir for 3 minutes, heat to 75°C, add sodium hydroxide solution to adjust the pH of the reaction solution to 11, continue stirring for 3 minutes, age for 25 minutes, separate and wash, and dry at 95°C for 11 hours 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 laser particle size distribution instrument measured the D50 of the high specific surface area silver particles of this embodiment to be 9.13 μm, the D100 to be 14.7 μm, and the dynamic nitrogen adsorption specific surface area instrument measured the specific surface area to be 15.4 m 2 / g, the direct recovery rate of silver powder is 99.6%.

[0037] Embodiment 4:

[0038] 1. Add 26% ammonia water to 6.0 mol / L hydrazine hydrate solution until the pH of the hydrazine hydrate solution is 12.

[0039] 2. At a temperature of 38°C, prepare an α-amino acid aqueous solution with a molar concentration of 0.024 mol / L.

[0040] 3. Use a peristaltic pump in a bidirectional manner to simultaneously add a hydrazine hydrate solution with a pH of 12 and a silver nitrate solution with a molar concentration of 2.4 mol / L to the α-amino acid solution within 10 minutes. After the addition is completed, stir for 2 minutes, heat to 75°C, add sodium hydroxide solution to adjust the pH of the reaction solution to 12, continue stirring for 2 minutes, age for 30 minutes, separate and wash, and dry at 100°C for 11 hours 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 laser particle size distribution instrument measured the high specific surface area silver particles of this embodiment with a D50 of 8.66 μm and a D100 of 15.6 μm. The dynamic nitrogen adsorption specific surface area instrument measured the specific surface area of ​​17.8 m 2 / g, the direct recovery rate of silver powder is 99.7%.

[0043] Please note that the technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above embodiments only express several implementation methods of the present application, and their descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several variations and improvements can be made, which all belong to the scope of protection of the present application. Therefore, the scope of protection of the patent in this application shall be based on the attached claims.

Claims

1. A method for preparing high specific surface area silver particles for low temperature sintering silver paste, characterized in that: The preparation method comprises the following steps: Step S1, adding ammonia water to a hydrazine hydrate solution having a molar concentration of 1.60 to 6.0 mol / L until the pH of the hydrazine hydrate solution is 10 to 13; Step S2, preparing an α-amino acid aqueous solution with a molar concentration of 0.012 to 0.048 mol / L at a temperature of 35° C. to 45° C.; Step S3, adding a hydrazine hydrate solution with a pH value of 10 to 13 and a silver nitrate solution with a molar concentration of 0.60 to 2.4 mol / L to the α-amino acid solution simultaneously within 8 to 12 minutes, stirring for 2 to 7 minutes, heating to 75 to 85° C., adding a sodium hydroxide solution to adjust the pH value of the reaction solution to 11 to 13, continuing to stir for 2 to 7 minutes, aging for 25 to 35 minutes, and finally separating, washing and drying to obtain silver particles with high specific surface area; In the 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.

2. The preparation method according to claim 1, characterized in that: In the 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 the 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 the 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.

7. The preparation method according to claim 6, characterized in that: In step S3, the high specific surface area silver particles have a D50 of 8.66 to 11.4 μm, a D100 of 14.7 to 15.7 μm, and a specific surface area of ​​12 to 17.8 m 2 / g.