KR102061719B1 - Silver powder and method for manufacturing the same - Google Patents

Abstract

Silver powder production method according to the present invention, the reaction solution manufacturing step (S21) for preparing a first reaction liquid containing silver ions, ammonia and organic acid alkali metal salt, and a second reaction liquid containing a reducing agent and sodium sulfite; And a silver salt reduction step (S2) including a precipitation step (S22) of reacting the first reaction solution and the second reaction solution to obtain silver powder.

Description

Silver powder and manufacturing method thereof {SILVER POWDER AND METHOD FOR MANUFACTURING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silver powder and a method for manufacturing the same, and more particularly, to a silver paste for a conductive paste for forming an electrode from an electronic component such as a solar cell electrode, an internal electrode of a multilayer capacitor, a conductor pattern of a circuit board, and the like. It is about a method.

The conductive paste is a paste in which electricity flows in the dried coating film having a coating ability capable of forming a coating film. The organic component is volatilized by the resin curing type and high temperature sintering, whereby the conductive filler is compressed by the curing of the resin to secure conduction. There is a sintered type in which conductive fillers are sintered to secure conduction. Among these, the sintered conductive paste is generally a fluid composition in which conductive powder (metal powder) is dispersed in a vehicle composed of a resin binder and a solvent, and is widely used for forming an electric circuit or forming an external electrode of a ceramic capacitor.

In general, well-dispersed silver powder of uniform size among metal powders is highly conductive, chemically stable, and inexpensive, and thus can be used as an important material for various electronic industries as conductive inks, pastes, and adhesives. have. Silver powder is divided into spherical, flake and agglomerated according to its shape, and silver powder of a suitable form is applied according to the application field.

Conventionally, the sintering start temperature has been lowered so that a rapid sintering start may occur in the process of sintering the conductive paste containing silver powder. To this end, the size of the silver powder is reduced or closed pores of a predetermined size or more are formed inside the particles as in the prior patent document (Korean Patent Laid-Open Publication No. 10-2014-7025084). On the other hand, in the solar cell is miniaturized the line width of the electrode in order to minimize the light loss, the silver powder of the conductive paste applied to it is also required to have a small size.

However, when the pores are formed inside the particles, a large amount of organic matter contained in the conductive paste may remain in the pores, and thus electrical conductivity may decrease after sintering. And since the ultrasonic equipment must be introduced separately to form voids inside the silver powder, the manufacturing cost may increase and the process may be complicated. In addition, if the size of the silver powder is small, the sintering speeds up, and the compatibility with the glass frit generally used for the conductive paste may decrease.

Accordingly, there is a demand for silver powder having a small size and excellent electrical conductivity and compatibility with the frit.

1. Korean Patent Publication No. 10-2014-0125418 (2014-10-28)

The present invention is a silver powder suitable for use in a high temperature sintered conductive paste of 600 ° C. or more, and the sintering starts at a relatively high temperature while having a small particle size, and may have a high shrinkage rate during sintering, It is to provide a silver powder excellent in compatibility with and a method for producing the same.

However, the objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

Silver powder production method according to the present invention, the reaction solution manufacturing step (S21) for preparing a first reaction liquid containing silver ions, ammonia and organic acid alkali metal salt, and a second reaction liquid containing a reducing agent and sodium sulfite; And a silver salt reduction step (S2) including a precipitation step (S22) of reacting the first reaction solution and the second reaction solution to obtain silver powder.

The reducing agent may comprise hydroquinone.

The reducing agent may further include hydrazine.

The amount of reducing agent may be greater than the amount of hydrazine.

The silver ions may be included in silver nitrate, and the sodium sulfite may be included in an amount of 18 to 60 g based on 120 ml of 500 g / L of silver nitrate.

The sodium sulfite may be included in an amount of 80 parts by weight to 120 parts by weight based on 100 parts by weight of the hydroquinone.

The silver ions may be included in silver nitrate, and the hydroquinone may be included in an amount of 18 to 60 g based on 120 ml of 500 g / L of silver nitrate.

The silver ions may be contained in silver nitrate, and the hydrazine may be included in an amount of 0.03 g or less with respect to 120 ml of 500 g / L of silver nitrate.

The silver powder according to the present invention has an average particle size of 0.5 to 2.5 μm, a sintering start temperature of 400 ° C. or higher at a temperature of 50 ° C./min, 800 ° C., and a shrinkage rate of 2.5 to 5 ° C. at a temperature of 400 ° C. to 600 ° C. % / min.

The silver powder may have a sintering start temperature of 400 to 450 ° C. at a temperature of 50 ° C./min and 800 ° C., and the silver powder may include sulfur (S).

According to the production method of the silver powder according to the present invention, when the average particle size (D50) is 0.5 to 2.5μm, 50 ℃ / min, contained in the conductive paste, the sintering start temperature is 400 ℃ or more at 800 ℃ elevated conditions ( For example, 400 to 450 ℃), the shrinkage rate in the interval 400 to 600 ℃ can be produced a silver powder of 2.5 to 5% / min. As described above, the silver powder has a small particle size and sintering starts at a relatively high temperature, whereas the sintering powder can have a large shrinkage rate during sintering so that the silver powder has excellent compatibility with the glass frit.

Figure 1 shows a scanning electron microscope (SEM) image of the silver powder prepared according to Example 1 of the present invention.
FIG. 2 is a graph showing dimension changes with temperature in Examples 1 to 3 and Comparative Example 1 by thermomechanical analysis (TMA).
3 is a graph showing the size change with temperature in Comparative Examples 1 to 3 by thermomechanical analysis (TMA).

Prior to describing the present invention in detail below, it is understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention, which is limited only by the scope of the appended claims. shall. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise indicated.

Throughout this specification and claims, unless otherwise indicated, the termcomprise, constitutes, and configure means to include the referenced article, step, or group of articles, and step, and any other article It is not intended to exclude a stage or group of things or groups of stages.

On the other hand, various embodiments of the present invention can be combined with any other embodiment unless clearly indicated to the contrary. Any feature indicated as particularly preferred or advantageous may be combined with any other feature and features indicated as preferred or advantageous. Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention and the effects thereof.

Method for producing a silver powder according to an embodiment of the present invention is a silver salt manufacturing step (S1); Silver salt reduction step (S2); Purification step such as filtration and washing (S3); And a surface treatment step (S4). The production method of silver powder according to the present invention necessarily includes a silver salt reduction step (S2), other steps can be omitted.

One. Silver salt manufacturing step (S1)

Silver salt preparation step (S1) according to an embodiment of the present invention to prepare a silver salt solution containing silver ions (Ag +) by acid treatment of silver (Ag +) in the form of ingots, ribs, granules As a step, the silver salt solution may be prepared by directly preparing a silver salt solution through this step, but commercially available silver nitrate may proceed to a later step using a silver salt complex or a silver intermediate solution.

2.  Silver salt reduction step (S2)

The silver salt reduction step (S2) according to an embodiment of the present invention is a step of depositing silver particles or silver powder by reducing silver ions by adding a reducing agent and ammonia to the silver salt solution. The reaction solution preparation step (S21) of preparing a first reaction solution containing silver ions, ammonia and an alkali metal alkali metal salt and a second reaction solution containing a reducing agent, and reacting the first reaction solution and the second reaction solution with silver powder The precipitation step S22 is obtained.

In the reaction solution preparation step (S21) according to an embodiment of the present invention, an alkali metal salt of organic acid is added to the silver salt solution containing silver ions, and the pH is adjusted with ammonia to prepare a first reaction solution.

The silver ions are not limited as long as they are in the form of silver cations. For example, it may be silver nitrate (AgNO ₃ ), a silver salt complex or a silver intermediate. Preferably, silver nitrate (AgNO ₃ ) is used. Hereinafter, the use of silver nitrate (AgNO ₃ ) containing silver ions will be described as an example. Hereinafter, the content of other components based on 120 mL of silver nitrate (AgNO ₃ ) of 500 g / L will be described.

In the present invention, by adding the organic acid alkali metal salt to the first reaction solution and adjusting the pH with ammonia, the shrinkage rate at a specific temperature range is high and the final shrinkage rate may be high.

The organic acid alkali metal salt may be acetic acid (CH ₃ COOH), formic acid (CH ₂ O ₂ ), oxalic acid (C ₂ H ₂ O ₄ ), lactic acid (C ₃ H ₆ O ₃ ), citric acid (C ₆ H ₈ O ₇ ), Fumaric Acid (C ₄ H ₄ O ₄ ), Citric Acid (C ₆ H ₈ O ₇ ), Butyric Acid (C ₄ H ₈ O ₂ ), Propionic Acid (CH ₃ CH ₂ COOH) and Uric Acid (C ₅ H ₄ N ₄ O ₃ Any one or more organic acids (short chain fatty acids) selected from the group consisting of) selected from the group consisting of lithium (Li), sodium (Na), potassium (K), calcium (Ca) and magnesium (Mg) One or more types of metal formed the salt. Preferably, at least one selected from the group consisting of potassium acetate (CH ₃ COOK), potassium formate (HCOOK) and potassium oxalate (C ₂ K ₂ O ₄ ) may be used.

The organic acid alkali metal salt is added in an amount of 7.5 to 45 g based on 120 ml of the 500 g / L silver nitrate (AgNO ₃ ). An organic acid alkali metal salt is added in the above range to provide an effect of increasing the shrinkage rate. If the amount is less than 7.5g, the effect is insignificant, and if it is added more than 45g, the effect may be similar to that added below.

Ammonia (NH ₃ ) may be used in the form of an aqueous solution, for example, when using a 25% aqueous ammonia solution may be added 105 to 525ml with respect to 120ml of 500g / L silver nitrate (AgNO ₃ ). When the ammonia is added in less than 105ml the size of the silver powder produced may be excessively reduced in size and angular, and when ammonia is added in excess of 525ml, the effect of reducing the heat shrinkage may not be sufficient. The ammonia includes its derivatives. By using ammonia, the pH condition at which reduction occurs in the precipitation step (S22) described later is adjusted to 8 to 11.

The first reaction solution containing silver ions, ammonia, and an organic acid alkali metal salt may be prepared in the form of a slurry by adding silver ions, ammonia, and an organic acid alkali metal salt to a solvent such as water, stirring, and dissolving the same. Can be.

Reaction liquid preparation step (S21) according to an embodiment of the present invention also prepares a second reaction liquid containing a reducing agent and sodium sulfite.

The reducing agent may include hydroquinone and may further include hydrazine. Here, the hydroquinone is a main reducing agent contained in an amount greater than hydrazine, and may be a material capable of effectively reducing silver ions contained in the silver salt solution. In particular, hydroquinone has an excellent reducing effect, and is suitable for realizing the effect described later by using with sodium sulfite. Hydrazine is added to control the size of the silver powder, for example, may help the silver powder to have a desired size (eg, 0.5 to 2.5 μm). If the hydrazine is contained in a large amount, the size of the silver powder may be reduced, which may lead to rapid sintering, thereby lowering the sintering initiation temperature. Therefore, the hydrazine is included in a smaller amount than the hydroquinone.

The additive including sodium sulfite is to increase the sintering start temperature to have a higher sintering start temperature (eg, 400 ° C. or higher, for example, 400 ° C. to 450 ° C.). Sodium sulfite is a material that can effectively improve the sintering onset temperature without significantly affecting silver powder or other properties. In particular, sodium sulfite serves to increase the sintering start temperature by binding to hydroquinone and being substituted with a sulfite-type reducing agent. The clear principle for this is not known, but it is expected that the added sulfite remains in the silver powder and slows the sintering. That is, in this invention, the additive which raises a sintering start temperature is added, and a sintering start temperature is raised contrary to the conventional. Thereby, it has a relatively high sintering start temperature and can improve compatibility with the glass frit contained in an electrically conductive paste.

At this time, the hydroquinone may be included as 18 to 60g with respect to 120ml of 500g / L silver nitrate (AgNO ₃ ) contained in the first reaction solution, hydrazine is 0.03g or less with respect to 120ml of 500g / L silver nitrate (AgNO ₃ ) ( For example, it may be included as 0.000012g to 0.03g). And sodium sulfite may be included in 18 to 60g with respect to 120ml of 500g / L silver nitrate (AgNO ₃ ). Alternatively, sodium sulfite may be included in an amount of 80 to 120 parts by weight (eg, 95 to 105 parts by weight, for example, 100 parts by weight) based on 100 parts by weight of hydroquinone.

If the content of hydroquinone is less than 18 g for 120 ml of 500 g / L silver nitrate (AgNO ₃ ), all silver ions may not be reduced, and if the nitric acid exceeds 60 g for 120 ml, the organic content may be higher than a desired standard.

When the content of hydrazine exceeds 0.03 g with respect to 120 ml of 500 g / L silver nitrate (AgNO ₃ ), there is a fear that the particles are too small to produce a powder in which fine particles are aggregated. And 500g / L of less than 0.000012g of silver nitrate (AgNO ₃ ) 120ml may not be sufficient to control the size of the silver powder.

If the content of sodium sulfite is less than 18 g for 120 ml of 500 g / L silver nitrate (AgNO ₃ ), the effect of increasing the sintering initiation temperature may not be sufficient, and 60 g for 120 ml of 500 g / L silver nitrate (AgNO ₃ ) If exceeded, the synergistic effect of the sintering start temperature is insignificant and the content of sulfur (S) is increased, which may adversely affect solar cell efficiency.

However, the present invention is not limited thereto, and the content of hydroquinone, hydrazine, sodium sulfite, and the like may be somewhat changed, and the type of reducing agent may also vary.

The second reaction solution containing a reducing agent may be prepared in an aqueous solution state by adding a reducing agent and an additive to a solvent such as water, stirring and dissolving it.

Precipitation step (S22) according to an embodiment of the present invention is a step of obtaining a silver powder by reacting the first reaction solution and the second reaction solution, stirring the first reaction solution prepared by the reaction solution preparation step (S21) The second reaction liquid can be added slowly or collectively and reacted in the state where it is. Preferably, the batch reaction may be completed in a short time to collectively add the bulk to prevent aggregation of the particles and to improve dispersibility. At this time, the surface treatment agent may be added together to perform the surface treatment simultaneously with the reduction reaction. For example, stearic acid (eg, stearic acid emulsion) may be used as the surface treating agent.

On the other hand, in the embodiment of the present invention does not exclude the addition of the dispersant to react in order to improve the dispersibility of the silver particles and prevent aggregation. Examples of dispersants include fatty acids, fatty acid salts, surfactants, organometallics, chelate formers and protective colloids.

However, when the dispersant is added, the remaining organic matter content may be increased, so it is desirable to control the particle size, the remaining organic matter content, and the crystallite diameter of the silver powder without adding the dispersant.

3. Purification step (S3)

Purification step (S3) according to an embodiment of the present invention is a silver salt reduction step (S2) after completing the silver particle precipitation reaction to remove and wash the silver powder dispersed in an aqueous solution or slurry using filtration and the like Step S31 is included. More specifically, after the silver particles in the silver powder dispersion are precipitated, the supernatant of the dispersion is discarded and filtered using a centrifuge, and the filter medium is washed with pure water. The washing process must be done by completely removing the wash water from which the powder has been washed. Therefore, the water content is reduced to less than 10%. It is also possible to optionally add the aforementioned dispersants to the reaction complete solution prior to filtration to prevent aggregation of the silver powder.

In addition, the purification step (S3) according to an embodiment of the present invention may further comprise a drying and disintegration step (S34) after washing.

4.  Surface treatment step (S4)

Surface treatment step (S4) according to an embodiment of the present invention is a step of hydrophobizing the hydrophilic surface of the silver powder, it may be made selectively. More specifically, after controlling the moisture content of the wet cake (wet cake) obtained after filtration to less than 10% can be added to the surface treatment agent for the surface treatment of the silver powder and the moisture content can be adjusted to 70% to 85%. Thereafter, silver powder can be obtained through drying and pulverization. When surface treatment of silver powder, the powder should be well dispersed, and the surface treatment is sufficient. If the water content is low, the dispersion efficiency is poor, so it is better to surface-treat a certain amount with water content.

According to the production method of the silver powder according to the present invention, the average particle size (D50) is 0.5 to 2.5 μm, using sodium sulfite as an additive while using hydroquinone and hydrazine as a reducing agent while adding an alkali metal salt of an organic acid. When included in the paste, the sintering start temperature is 400 ° C. or higher (for example, 400 to 450 ° C.) at 50 ° C./min and 800 ° C., and the shrinkage rate at 400 ° C. to 600 ° C. is 2.5 to 5% /. A silver powder of min (eg, 3 to 5% / min) can be prepared. As described above, the silver powder has a small particle size and sintering starts at a relatively high temperature, whereas the sintering powder can have a large shrinkage rate during sintering so that the silver powder has excellent compatibility with the glass frit. Silver powder formed using sodium sulfite as an additive or silver powder containing sulfur (S) can be detected by a carbon / sulfur analyzer (CS analyzer).

In this case, the silver powder may not have voids therein. This eliminates the need for a separate equipment and process for forming the pores, and does not form the pores, thereby effectively reducing the organic content remaining therein and having a high shrinkage rate. For example, the shrinkage rate may be 20 to 30%.

Examples and Comparative Examples

(1) Example 1

120 g of pure water at room temperature was charged with 120 g of 500 g / L silver nitrate, 22 g of oxalic acid, and 190 ml of ammonia (concentration 25%), followed by stirring to prepare a first reaction solution (see Table 1). Meanwhile, 18 g of hydroquinone, 0.008 g of hydrazine, and 18 g of sodium sulfite were added to 1000 g of pure water at room temperature, followed by stirring to prepare a second reaction solution (see Table 1).

Subsequently, the 1st reaction liquid was made to stir, the 2nd reaction liquid was added to this 1st reaction liquid collectively, and it stirred for 10 more minutes after completion | finish of addition, and the particle | grains were grown in the mixed liquid. 10 seconds after the second reaction solution was added, stearic acid emulsion was added as a surface treating agent, and surface treatment was performed simultaneously with the synthesis. Then, stirring was stopped, the particles in the mixed solution were allowed to settle, the supernatant of the mixed solution was discarded, the mixed solution was filtered using a centrifugal separator, the media was washed with pure water, dried, and silver powder was obtained.

(2) Example 2

120 g of pure water at room temperature was charged with 120 g of 500 g / L silver nitrate, 22 g of oxalic acid, and 190 ml of ammonia (concentration 25%), followed by stirring to prepare a first reaction solution (see Table 1). Meanwhile, 18 g of hydroquinone, 0.010 g of hydrazine and 18 g of sodium sulfite were added to 1000 g of pure water at room temperature, followed by stirring to prepare a second reaction solution (see Table 1).

Subsequently, the 1st reaction liquid was made to stir, the 2nd reaction liquid was added to this 1st reaction liquid collectively, and it stirred for 10 more minutes after completion | finish of addition, and the particle | grains were grown in the mixed liquid. 10 seconds after the second reaction solution was added, stearic acid emulsion was added as a surface treating agent, and surface treatment was performed simultaneously with the synthesis. Then, stirring was stopped, the particles in the mixed solution were allowed to settle, the supernatant of the mixed solution was discarded, the mixed solution was filtered using a centrifugal separator, the media was washed with pure water, dried, and silver powder was obtained.

(3) Example 3

In a pure water 720g at room temperature, 120g of 500g / L silver nitrate, 22g of oxalic acid, 190ml of ammonia (concentration of 25%) was added, stirred, and dissolved to prepare a first reaction solution. Meanwhile, 18 g of hydroquinone, 0.012 g of hydrazine, and 18 g of sodium sulfite were added to 1000 g of pure water at room temperature, followed by stirring to prepare a second reaction solution (see Table 1).

Subsequently, the 1st reaction liquid was made to stir, the 2nd reaction liquid was added to this 1st reaction liquid collectively, and it stirred for 10 more minutes after completion | finish of addition, and the particle | grains were grown in the mixed liquid. 10 seconds after the second reaction solution was added, stearic acid emulsion was added as a surface treating agent, and surface treatment was performed simultaneously with the synthesis. Then, stirring was stopped, the particles in the mixed solution were allowed to settle, the supernatant of the mixed solution was discarded, the mixed solution was filtered using a centrifugal separator, the media was washed with pure water, dried, and silver powder was obtained.

(1) Comparative Example 1

120 g of pure water at room temperature was charged with 120 g of 500 g / L silver nitrate, 22 g of oxalic acid, and 190 ml of ammonia (concentration 25%), followed by stirring to prepare a first reaction solution (see Table 1). Meanwhile, 18 g of hydroquinone and 0.008 g of hydrazine were added to 1000 g of room temperature pure water, followed by stirring to prepare a second reaction solution (see Table 1). Unlike Examples 1-3, no sodium sulfite was added.

Subsequently, the 1st reaction liquid was made to stir, the 2nd reaction liquid was added to this 1st reaction liquid collectively, and it stirred for 10 more minutes after completion | finish of addition, and the particle | grains were grown in the mixed liquid. 10 seconds after the second reaction solution was added, stearic acid emulsion was added as a surface treating agent, and surface treatment was performed simultaneously with the synthesis. Then, stirring was stopped, the particles in the mixed solution were allowed to settle, the supernatant of the mixed solution was discarded, the mixed solution was filtered using a centrifugal separator, the media was washed with pure water, dried, and silver powder was obtained.

(2) Comparative Example 2

120 g of pure water at room temperature was charged with 120 g of 500 g / L silver nitrate, 22 g of oxalic acid, and 190 ml of ammonia (concentration 25%), followed by stirring to prepare a first reaction solution (see Table 1). Meanwhile, 18 g of hydroquinone, 0.008 g of hydrazine, and 5 g of sodium sulfite were added to 1000 g of room temperature pure water, followed by stirring to prepare a second reaction solution (see Table 1).

Subsequently, the 1st reaction liquid was made to stir, the 2nd reaction liquid was added to this 1st reaction liquid collectively, and it stirred for 10 more minutes after completion | finish of addition, and the particle | grains were grown in the mixed liquid. 10 seconds after the second reaction solution was added, stearic acid emulsion was added as a surface treating agent, and surface treatment was performed simultaneously with the synthesis. Then, stirring was stopped, the particles in the mixed solution were allowed to settle, the supernatant of the mixed solution was discarded, the mixed solution was filtered using a centrifugal separator, the media was washed with pure water, dried, and silver powder was obtained.

(3) Comparative Example 3

120 g of pure water at room temperature was charged with 120 g of 500 g / L silver nitrate, 22 g of oxalic acid, and 190 ml of ammonia (concentration 25%), followed by stirring to prepare a first reaction solution (see Table 1). Meanwhile, 18 g of hydroquinone, 0.008 g of hydrazine, and 10 g of sodium sulfite were added to 1000 g of pure water at room temperature, followed by stirring to dissolve the second reaction solution (see Table 1).

Subsequently, the 1st reaction liquid was made to stir, the 2nd reaction liquid was added to this 1st reaction liquid collectively, and it stirred for 10 more minutes after completion | finish of addition, and the particle | grains were grown in the mixed liquid. 10 seconds after the second reaction solution was added, stearic acid emulsion was added as a surface treatment agent, and the surface treatment was performed simultaneously with the synthesis. Then, stirring was stopped, the particles in the mixed solution were allowed to settle, the supernatant of the mixed solution was discarded, the mixed solution was filtered using a centrifugal separator, the media was washed with pure water, dried, and silver powder was obtained.

First reaction solution Second reaction solution pure
(g) 500 g / L
lunar caustic
(ml) ammonia
(ml) Oxalic acid
(g) pure
(g) Hydroquinone (g) Hydrazine
(g) Sodium sulfite (g) Example 1 720 120 190 22 1000 18 0.008 18 Example 2 720 120 190 22 1000 18 0.010 18 Example 3 720 120 190 22 1000 18 0.012 18 Comparative Example 1 720 120 190 22 1000 18 0.008 - Comparative Example 2 720 120 190 22 1000 18 0.008 5 Comparative Example 3 720 120 190 22 1000 18 0.008 10

Experimental Example

(1) Scanning electron microscope (SEM) size measurement

The silver powders prepared according to the above Examples and Comparative Examples were measured using a scanning electron microscope manufactured by JEOL, and then averaged by measuring diameter sizes of 100 powders, and then measuring the SEM size (μm). Table 2 shows. An SEM image of the silver powder prepared according to Example 1 is shown in FIG. 1.

(2) TMA (Thermogravimetric analyzer)

87 g of silver powder prepared according to Examples and Comparative Examples, 1 g of 10% ethyl cellulose resin (STD200), 12 g of an organic solvent (diethylene glycol monoethyl ether acetate) were mixed and kneaded with a 3-roll mill to prepare a paste.

Sintering start temperature (℃), 400 ℃ to 600 ℃ when the paste is prepared on an alumina substrate with a 200 μm ² area and heated up to 800 ° C. at a temperature rising rate of 50 ° C./min through TMA (Thermomechanical Analysis) The shrinkage rate (% / min) at and measured in Figures 2 and 3, and Table 2 below. For the sake of clarity, FIGS. 2 and 3 show Comparative Examples 1 and 3, and FIG. 3 shows Comparative Examples 1 to 3, respectively.

Average particle size [Dsem]
(Μm) Sintering start temperature (℃) Shrinkage Rate (% / min) Example 1 1.50 466.58 4.85 Example 2 1.06 418.37 3.40 Example 3 0.70 407.91 4.43 Comparative Example 1 0.97 326.30 4.29 Comparative Example 2 1.25 349.09 4.21 Comparative Example 3 1.25 399.60 3.06

As shown in Table 2, it can be seen that the silver powder prepared according to the present invention may have a size of 0.5 to 2.5 μm to correspond to a fine line width, and higher sintering than the silver powder prepared according to Comparative Examples 1 to 3 It can be seen that the start temperature (that is, the sintering start temperature of 400 ℃ or more) and a sufficiently large shrinkage rate (ie, 2.5% / min or more, for example, 3 to 5% / min) together.

Accordingly, when the front electrode of the solar cell is formed by using the conductive paste including the silver powder according to the present invention, it may be suitably used to form a fine pattern of 40 μm or less due to a high shrinkage ratio after firing. In addition, as shown in FIG. 1, it can be seen that there is no void in the silver powder particles (wherein, the void has a shortest diameter of 50 nm or more). As a result, the amount of organic matter that may be present in the pores may be reduced, and the conductive film formed by the high plastic density may have excellent electrical conductivity.

The features, structures, effects, and the like illustrated in the above-described embodiments may be combined or modified with respect to other embodiments by those skilled in the art to which the embodiments belong. Therefore, contents related to such combinations and modifications should be construed as being included in the scope of the present invention.

Claims (10)

A reaction solution preparation step (S21) of preparing a first reaction solution including silver ions, ammonia, and an organic acid alkali metal salt, and a second reaction solution including a reducing agent and sodium sulfite; And
And a silver salt reduction step (S2) comprising a precipitation step (S22) of reacting the first reaction solution and the second reaction solution to obtain a silver powder.
The reducing agent comprises hydroquinone and hydrazine,
The silver ions are contained in silver nitrate,
The sodium sulfite is contained in 18 to 60g per 120ml of 500g / L silver nitrate,
The hydroquinone is contained in 18 to 60g with respect to 120ml of 500g / L silver nitrate,
The hydrazine is a silver powder manufacturing method, characterized in that it comprises less than 0.03g per 120ml of silver nitrate of 500g / L,
The average particle size is 0.5 to 2.5 μm, the sintering start temperature is 400 ℃ or more at 50 ℃ / min, 800 ℃ elevated temperature conditions, the shrinkage rate in the 400 ~ 600 ℃ section is 2.5 to 5% / min based on the length Silver powder manufacturing method
The method of claim 1,
The method for producing silver powder, characterized in that the sodium sulfite is contained in an amount of 80 to 120 parts by weight based on 100 parts by weight of the hydroquinone.
The method of claim 1,
A method for producing silver powder without voids having a shortest diameter of 50 nm or more in pores appearing in the SEM image.
The method of claim 1,
The silver powder is a method of producing silver powder, characterized in that containing sulfur (S). delete delete delete delete delete delete

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