A low-temperature sinterable silver powder and its preparation method and application

Abstract

The present invention discloses a low-temperature sinterable silver powder, a preparation method thereof, and an application thereof. The silver powder has a particle size of 80-100 nm and a sintering temperature of 120-150°C. The preparation method comprises the following steps: S1. dispersing a reducing agent in a dispersant solution and adjusting the pH to 5-10 to obtain a mixed solution; S2. dropwise adding a silver nitrate solution to the mixed solution in two stages at different liquid addition flow rates and liquid addition times to obtain a reaction mixture; S3. washing and centrifuging the reaction mixture, and then drying the reaction mixture to obtain the low-temperature sinterable silver powder. The silver powder has a small particle size, good dispersibility, and a low sintering temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic pastes, and in particular to a low-temperature sinterable silver powder and a preparation method and application thereof. Background Art

[0002] Electronic paste is the most fundamental functional material in the electronics industry. Silver powder, as the conductive phase in electronic paste, boasts high conductivity and high efficiency. It is widely used in a wide range of fields, including aviation, aerospace, computers, photovoltaics, and the civilian market, and plays a vital role in the electronics, information, and energy sectors. The further development of the touch screen industry, in particular, places higher demands on the performance of silver paste for touch screen circuits.

[0003] Silver powder, a key raw material for silver paste, has a significant impact on its performance, depending on its particle size, morphology, particle size distribution, tap density, and surface condition. Currently, silver powder preparation methods include physical and chemical methods. Chemical methods are the primary method used for large-scale production due to their low production cost and ease of control.

[0004] However, the silver powder prepared by the current mainstream chemical method has a large particle size, is highly dependent on crystal seeds, and has a high sintering temperature, which limits its application range. Summary of the Invention

[0005] In view of this, the present application provides a low-temperature sinterable silver powder and its preparation method and application, which has small particle size, good dispersibility and low sintering temperature.

[0006] In order to achieve the above technical objectives, this application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a low-temperature sinterable silver powder, the particle size of the silver powder is 80-100 nm, and the sintering temperature of the silver powder is 120-150°C.

[0008] In a second aspect, the present application provides a method for preparing low-temperature sinterable silver powder, comprising the following steps:

[0009] S1. The reducing agent is dispersed in the dispersant solution and the pH is adjusted to 5-10 to obtain a mixed solution;

[0010] S2. In the mixed solution, silver nitrate solution was added dropwise in two stages at different liquid addition rates and addition times to obtain a reaction mixture;

[0011] S3. The reaction mixture is washed and centrifuged, and then dried to obtain low-temperature sinterable silver powder.

[0012] Preferably, the two stages include a seed crystal formation stage and a powder growth stage, the liquid addition time in the powder growth stage is longer than the liquid addition time in the crystal formation stage, and the liquid addition flow rate in the crystal formation stage is greater than the liquid addition flow rate in the powder growth stage.

[0013] Preferably, the liquid addition flow rate during the powder growth stage is 2-10 times the liquid addition flow rate during the seed formation stage.

[0014] Preferably, the ratio of the liquid addition time in the seed crystal formation stage to the liquid addition time in the powder growth stage is 3-10:90-97.

[0015] Preferably, the molar ratio of the dispersant to the silver nitrate is 0.1:1-5.

[0016] Preferably, the concentration of the reducing agent is 0.5-2 mol / L, and the concentration of the silver nitrate is 1-5 mol / L.

[0017] Preferably, the drying temperature is 45-70°C.

[0018] Preferably, the reducing agent includes one or more of ascorbic acid, formaldehyde, and hydrazine hydrate.

[0019] In a third aspect, the present application provides an electronic paste containing low-temperature sinterable silver powder.

[0020] The beneficial effects of this application are as follows:

[0021] This solution uses the principle that the reducing agent has different reducing strengths at different pH values to form self-seed crystals, thus achieving the goal of generating ultrafine nano-silver powder without adding seed crystals to the reaction solution.

[0022] By controlling the amount of dispersant added, the duration and method of adding silver nitrate, and thus the rate at which silver ions are reduced, the probability of collision between generated silver particles is synergistically reduced, effectively solving the aggregation problem of silver powder during the preparation process.

[0023] By adjusting the liquid addition time and liquid addition flow rate during the seed formation stage and the powder growth stage, the particle size of the final prepared silver powder can be controlled between 80-100nm, avoiding tedious operations and material preparation problems;

[0024] By controlling the preparation process parameters, the process has very good stability, and large-scale production of this type of silver powder can be achieved, reaching more than 5kg / batch. At the same time, the raw materials used in the production of this type of silver powder are cheap and the waste liquid treatment is relatively simple. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0026] The present application provides a low-temperature sinterable silver powder, the particle size of the silver powder is 80-100nm, and the sintering temperature of the silver powder is 120-150°C.

[0027] The present application provides a method for preparing low-temperature sinterable silver powder, comprising the following steps:

[0028] S1. The reducing agent is dispersed in the dispersant solution and the pH is adjusted to 5-10 to obtain a mixed solution;

[0029] S2. In the mixed solution, silver nitrate solution was added dropwise in two stages at different liquid addition rates and addition times to obtain a reaction mixture;

[0030] S3. The reaction mixture is washed and centrifuged, and then dried to obtain low-temperature sinterable silver powder.

[0031] In this method, a strategy of self-seed formation in the early stage and growth in the later stage is adopted, which can spontaneously form a large number of highly active seed crystals, thereby reducing the particle size: the reducing agent forms seed crystals on the principle of different reducing strengths at different pH values, thereby achieving the purpose of generating ultrafine nano silver powder without adding seed crystals to the reaction solution, and then adjusting the addition flow rate and addition time of silver nitrate to control the particle size of the final prepared silver powder, so that the silver powder particle size is 80-100nm and the sintering temperature is 120-150℃.

[0032] The substance used to adjust the pH is one of sodium hydroxide and potassium hydroxide; the reducing agent includes one or more of ascorbic acid, formaldehyde and hydrazine hydrate.

[0033] The two stages mentioned in step S2 include a crystal seed formation stage and a powder growth stage. The purposes of crystal seed formation and powder growth are achieved respectively by different liquid addition flow rates and liquid addition times. Both stages are reduction reactions between the reducing agent and silver nitrate. The liquid addition time in the powder growth stage is longer than the liquid addition time in the crystal formation stage, and the liquid addition flow rate in the crystal formation stage is longer than the liquid addition flow rate in the powder growth stage.

[0034] In some embodiments, the concentration of the reducing agent is 0.5-2 mol / L, and the concentration of silver nitrate is 1-5 mol / L. The reducing agent with the above concentration and silver nitrate are used as raw materials to carry out the reactions of step S1 and step S2. The liquid addition flow rate in the powder growth stage is 2-10 times the liquid addition flow rate in the seed formation stage. The ratio of the liquid addition time in the seed formation stage to the liquid addition time in the powder growth stage is 3-10:90-97. By adjusting the above process parameters, the controllable preparation of silver powder size can be achieved, and an ultra-low temperature sinterable silver powder product can be obtained.

[0035] The molar ratio of dispersant to silver nitrate is 0.1:1-5. With the help of dispersant, the reduction rate of silver ions can be coordinated to reduce the probability of collision between generated silver particles, effectively solving the dispersion problem of silver powder in the preparation process.

[0036] The drying temperature is 45-70℃. The properties of the product will not be affected if the product is dried within this temperature range.

[0037] The present application provides an electronic paste containing low-temperature sinterable silver powder.

[0038] Example 1

[0039] A method for preparing low-temperature sinterable silver powder comprises the following steps:

[0040] S1 0.1mol / L of polyvinylpyrrolidone K60 was placed in a reaction vessel, fully dissolved, 1mol / L of L- ascorbic acid was added, and then sodium hydroxide reagent was added to adjust the pH of the solution to 10 to obtain a mixed solution;

[0041] S2. Then, a 1 mol / L silver nitrate solution was added dropwise to the mixed solution obtained in step S1 in two stages at different addition rates and addition times: the addition rate during the seed formation period was 50 mL / min, the addition time during the seed formation period was 10 min, and the addition rate during the powder growth period was 200 mL / min, the addition time during the powder growth period was 90 min, to obtain a reaction mixture;

[0042] S3. After the reaction is completed, the product is washed with deionized water and ethanol respectively, and then the solid and liquid phases are separated by a centrifuge, and then dried in an oven set at a temperature of 80°C to obtain the final silver powder product.

[0043] Example 2

[0044] A method for preparing low-temperature sinterable silver powder, wherein the other steps are the same as those in Example 1, except that in step S2, the droplet addition rate during the powder growth period is 500 mL / min.

[0045] Example 3

[0046] A method for preparing low-temperature sinterable silver powder, wherein the other steps are the same as those in Example 1, except that in step S2, the droplet addition rate during the seed crystal formation period is 100 mL / min.

[0047] Example 4

[0048] A method for preparing low-temperature sinterable silver powder, wherein the other steps are the same as those in Example 1, except that in step S2, the droplet addition rate during the seed crystal formation period is 20 mL / min.

[0049] Example 5

[0050] A method for preparing low-temperature sinterable silver powder. The other steps are the same as those in Example 1, except that the concentration of polyvinylpyrrolidone K60 is 0.02 mol / L, the liquid addition time during the seed formation period is 3 minutes, and the liquid addition time during the powder growth period is 97 minutes.

[0051] Example 6

[0052] A method for preparing low-temperature sinterable silver powder. The other steps are the same as those in Example 1, except that the concentration of polyvinylpyrrolidone K60 is 0.2 mol / L, the liquid addition time during the seed formation period is 3 minutes, and the liquid addition time during the powder growth period is 97 minutes.

[0053] Example 7

[0054] A method for preparing low-temperature sinterable silver powder, wherein the other steps are the same as those in Example 1, except that the pH value is 5.

[0055] Comparative Example 1

[0056] A method for preparing silver powder, wherein the other steps are the same as those in Example 1, except that the pH in step S1 is 4.

[0057] Comparative Example 2

[0058] A method for preparing silver powder, wherein the other steps are the same as those in Example 1, except that the pH in step S1 is 11.

[0059] Comparative Example 3

[0060] A method for preparing silver powder, wherein the other steps are the same as those in Example 1, except that all the silver nitrate solution is uniformly added dropwise to the mixed solution in step S1, the addition speed is 50 mL / min, and the addition time is 100 min.

[0061] The particle size D50 of the silver powder prepared in Examples 1-7 and Comparative Examples 1-3 was analyzed by SEM electron microscopy, and the sintering temperature of the silver powder prepared in Examples 1-7 and Comparative Examples 1-3 was measured by TMA. The results are shown in Table 1.

[0062] Table 1 Test results of different silver powders

[0063]

[0064]

[0065] The data show that when the pH exceeds the range limited by 5-10, the silver powder obtained in Comparative Examples 1-2 has a larger D50 than the silver powder in Examples 1-7, and the sintering temperature is higher; while in Comparative Example 3, silver nitrate is added dropwise at the same rate, and the D50 particle size and sintering temperature are slightly increased compared with Examples 1-7; it can be seen from Examples 1, 3, and 4 that within the scope of the present application, the optimal rate of addition of liquid during the powder growth period is 4 times the rate of addition of liquid during the seed formation period; it can be seen from Examples 1 and 2 that as the rate of addition of liquid during the powder growth period increases, the D50 particle size and sintering temperature increase.

[0066] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing low-temperature sinterable silver powder, characterized in that: The following steps are involved: S1. The reducing agent is dispersed in the dispersant solution and the pH is adjusted to 5-10 to obtain a mixed solution; S2. In the mixed solution, silver nitrate solution was added dropwise in two stages at different liquid addition rates and addition times to obtain a reaction mixture; S3. Clean and centrifuge the reaction mixture, and then dry it to obtain the low-temperature sinterable silver powder; the two stages include a seed formation stage and a powder growth stage, and the liquid addition flow rate in the powder growth stage is 2-10 times the liquid addition flow rate in the seed formation stage; the ratio of the liquid addition time in the seed formation stage to the liquid addition time in the powder growth stage is 3-10:90-97; the molar ratio of the dispersant to silver nitrate is 0.1:1-5; the concentration of the reducing agent is 0.5-2 mol / L, and the concentration of the silver nitrate is 1-5 mol / L; the drying temperature is 45-70°C; the reducing agent includes one or more of ascorbic acid, formaldehyde, and hydrazine hydrate.

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