JP4109520B2 - Low cohesive silver powder, method for producing the low cohesive silver powder, and conductive paste using the low cohesive silver powder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The invention according to the present application relates to a low-aggregation silver powder and a method for producing the low-aggregation silver powder.
[0002]
[Prior art]
In recent years, silver powder has been frequently used as a wiring circuit, an electrode and the like for electronic devices. In general, silver powder is processed into a conductive paste and baked into a circuit or electrode shape. At this time, recent electric and electronic devices are required to be downsized in response to the trend of lightening, thinning, and miniaturization. Accordingly, it has been demanded that a circuit having a high wiring density can be formed even when a circuit or the like is drawn using a conductive paste containing silver powder.
[0003]
Therefore, in order to realize the shape of a fine circuit, etc. with respect to the silver powder, the powder particles of the silver powder are fine, the low cohesiveness to reduce the paste viscosity when processed into a conductive paste, the circuit after firing There has been a demand for heat shrinkability to minimize the dimensional change of the shape. For the production of these silver powders, a wet reduction method and an atomization method classified as a dry method have been employed.
[0004]
[Patent Document 1]
JP 2001-107101 A [Patent Document 2]
Japanese Patent Laid-Open No. 2000-265202
[Problems to be solved by the invention]
However, the silver powder obtained by either the wet reduction method or the atomization method has advantages and disadvantages. In other words, the silver powder obtained using the wet reduction method has the characteristics of being fine and highly dispersible, and is excellent for routing fine high-density wiring circuits and the like after being processed into a conductive paste. It is. However, since the silver powder obtained by the wet reduction method has a small crystallite diameter, the dimensional shrinkage during firing is increased.
[0006]
On the other hand, since the silver powder obtained by the atomizing method has a large crystallite diameter, the dimensional shrinkage during firing is small, and a wiring circuit or the like having excellent dimensional accuracy can be formed. However, a drawback of silver powder obtained by the atomizing method can not particle size is an average particle size D ₅₀ by laser diffraction scattering particle size distribution measuring method to obtain the following fine silver powder 5 [mu] m, are routed processing high-density wiring It was difficult.
[0007]
As can be seen from the above, there was no fine silver powder having excellent dispersibility (low cohesion) and a large crystallite size at the same time. Therefore, the supply of new silver powder used for forming conductors such as high-density wiring circuits and electrodes has been desired from the market.
[0008]
[Means for Solving the Problems]
Therefore, the inventors of the present invention have conceived that by adopting the production method described below, (1) low agglomeration and (2) a large crystallite size similar to silver powder obtained by the atomization method can be achieved simultaneously. This made it possible to provide fine silver powder that has never existed before.
[0009]
The fine silver powder according to the present invention is “a silver powder obtained using a wet reduction method, having an average particle diameter D ₅₀ of 0.1 μm to 3 μm by a laser diffraction scattering type particle size distribution measurement method, and the average the value of cohesion with the average particle diameter _{D IA} obtained by a particle size _{D 50} and the image analysis represented by _D 50 _{/ D IA} is Ri der 5.0 or less and the crystallite diameter is 20nm or more Oh, wherein the Rukoto low cohesion silver powder. "is.
[0010]
Since the low-aggregating silver powder referred to here is first a fine particle, when the average particle diameter D ₅₀ obtained by the atomizing method is 5 μm or more, the average particle diameter D ₅₀ obtained by the spray pyrolysis method exceeds 2 μm. Even in comparison, the average particle diameter D ₅₀ is in a smaller range of 0.1 μm to 3 μm. When the average particle diameter D ₅₀ is less than 0.1 [mu] m, in case of processing in the conductive paste, mixing and stirring of the binder resin becomes poor, it is the homogeneous mixing becomes difficult. On the other hand, if the average particle diameter D ₅₀ exceeds 3 μm, the product cannot meet the market demand, and by adopting the manufacturing method described below, the particle diameter is inevitably in the range of 2 μm or less.
[0011]
Then, it will be described cohesion represented by _D 50 _{/ D IA} with an average particle diameter _{D IA} obtained by the average particle diameter _{D 50} and the image analysis. The degree of aggregation is an index for capturing the dispersibility of silver powder particles, as will be understood from the following description. In addition, the image analysis of the silver dust observed using the scanning electron microscope (SEM) in this specification is circular as the circularity threshold value 10 and the overlapping degree 20 using Asahi Engineering Co., Ltd. IP-1000PC. Particle analysis was performed to determine the average particle diameter _DIA .
[0012]
That is, the value of the average particle diameter D ₅₀ obtained by using a laser diffraction scattering particle size distribution measuring method, truly be said to be other than direct observation every single size of particulate. This is because most of the silver particles constituting the silver powder are not so-called monodispersed powders in which individual particles are completely separated, but a plurality of powder particles are aggregated and aggregated. In the laser diffraction / scattering particle size distribution measurement method, it can be said that the average particle size is calculated by capturing the aggregated particles as one particle (aggregated particles).
[0013]
On the other hand, since the average particle diameter _DIA obtained by image-processing the observation image of the silver powder observed using a scanning electron microscope (SEM) is obtained directly from the SEM observation image, the primary particles On the other hand, the presence of the agglomerated state of the powder particles is not reflected at all.
[0014]
Therefore, using the value of the average particle diameter D ₅₀ or the value of the average particle diameter D _IA that has been widely used alone to compare with the viscosity of the conductive paste, in any case, the conductive paste It does not accurately reflect the inherent state of the silver powder used in the manufacture of.
[0015]
Results considered as above, the present inventors have found that, by using the average particle diameter D _IA obtained by an average particle size D ₅₀ and the image analysis of a laser diffraction scattering particle size distribution measurement method, at D _{50 /} D _IA The calculated value was taken as the degree of aggregation. That is, assuming that the values of D ₅₀ and D _IA can be measured with the same accuracy in the same lot of silver powder, the value of D ₅₀ that reflects the presence of agglomerated state in the measured value is It is considered that the value is larger than the value of _DIA . At this time, the value of D _50, if the granular state of aggregation of the silver powder totally eliminated, Yuki approaching the value of the infinitely D _IA, the value of a degree of aggregation D _{50 /} D _IA, approaches 1 It will be. It can be said that it is a monodispersed powder in which the agglomeration state of the powder is completely lost when the aggregation degree becomes 1.
[0016]
Therefore, the present inventors examined the correlation between the degree of aggregation and the silver paste produced using silver powder of each degree of aggregation. As a result, a very good correlation was obtained. As can be seen from this, it can be determined that if the degree of aggregation of silver powder is controlled, the viscosity of the conductive paste produced using the silver powder can be controlled.
[0017]
Moreover, the aggregation degree calculated | required by calculation may show a value less than one. Theoretically, in the case of a true sphere, the value is not less than 1. However, in reality, since it is not a true sphere, a value less than 1 seems to be obtained as the degree of aggregation. If the value of the degree of aggregation represented by D ₅₀ / D _IA is 5.0 or less, it can be determined that the silver powder has excellent dispersibility, and if the resin composition of the conductive paste is the same, there is no conventional one. This makes it possible to reduce the viscosity of the conductive paste at the level, and facilitate the drawing of fine high-density circuits and the like.
[0018]
Furthermore, the low cohesive silver powder obtained by the production method according to the present invention is also characterized by having a large crystallite diameter of 20 nm or more equivalent to that obtained by the atomization method. Having a large crystallite diameter means that the silver powder processed into a conductive paste has excellent heat shrinkage resistance when fired, so it is possible to reduce the shape change of drawn circuits, electrodes, etc. It becomes.
[0019]
Next, the manufacturing method of the low cohesion silver powder which concerns on this invention is demonstrated. In short, this production method is a wet reduction method in which a silver chelate complex slurry is reacted with a reducing agent. This manufacturing method is performed according to the following procedure.
[0020]
In the step (1), an ethylenediaminetetraacetate solution is added to a silver nitrate solution having a concentration of 80 g / l to 120 g / l to prepare a silver chelate complex slurry of silver and ethylenediaminetetraacetate. The silver chelate complex slurry used here is obtained by adding an ethylenediaminetetraacetate solution as a complexing agent to a silver nitrate solution having a concentration of 80 g / l to 120 g / l. Here, the addition amount of ethylenediaminetetraacetate that forms a complex with the silver ion serving as the supply source with the silver nitrate solution concentration is determined in consideration of the silver nitrate concentration and the complex forming ability.
[0021]
Therefore, what is important is the silver ion concentration in the silver nitrate solution. If the range of the silver ion concentration is clarified, it can be said that the addition amount of ethylenediaminetetraacetate is naturally determined. When the concentration of the silver nitrate solution shown here is less than 80 g / l, the amount of silver powder produced is small and it cannot be used industrially, and the burden of waste water treatment simply increases. On the other hand, when the concentration of the silver nitrate solution exceeds 120 g / l, the particle size of the silver powder generated by the reduction reaction increases and the particle size distribution tends to become broader.
[0022]
In step (2), the silver chelate complex slurry is filtered and washed to collect the silver chelate complex. The filtration method is not particularly limited and may be performed according to a conventional method. The silver chelate complex separated by filtration is washed from the viewpoint of preventing the solution from being brought into the subsequent process, but is usually washed with water.
[0023]
In step (3), pure water is added to the silver chelate complex to form a reslurry. The reason for making the reslurry in this way is to facilitate mixing with the reducing agent.
[0024]
In the step (4), a reducing agent is added to the silver chelate complex-containing slurry to cause a slow reduction reaction, thereby obtaining fine silver powder. Here, it is preferable to use a reducing agent having a weak reducing power. However, when a relatively strong reducing agent is used, the reaction solution temperature must be lowered. When a strong reducing agent is reacted at a high temperature, silver powder is rapidly generated, and the resulting silver powder has a large particle size and a small crystallite diameter, resulting in silver powder that is contrary to the object of the present invention. As this reducing agent, sulfites such as potassium sulfite, glucose, hydrazine, hydroquinone, formalin, ascorbic acid, hypophosphorous acid, SBH, sucrose, fructose, menthol, polyol and the like can be used. Among these, sulfites such as potassium sulfite and glucose are preferably used from the viewpoint of quality stability.
[0025]
Moreover, this reducing agent may be used individually by 1 type, or may mix and use 2 or more types. For example, potassium sulfite and glucose are mixed and used. Potassium sulfite and glucose are reducing agents that have a weak reducing power, but there is a difference in reducing power between them, and they can be used for the purpose of fine-tuning the rate of silver reduction. Moreover, as the temperature used for the reduction, a range of 45 ° C. to 55 ° C. around 50 ° C. seems to give the best results. When the reduction temperature is less than 45 ° C., the crystallite diameter becomes small, and when it exceeds 55 ° C., atomization tends to be difficult.
[0026]
In the step (5), the fine silver powder is collected by filtration, washed and dried to obtain a low-aggregation silver powder. These steps can be understood by those skilled in the art without any particular explanation, and the present invention is also carried out in accordance with conventional methods.
[0027]
With the manufacturing method as described above, it is possible to obtain fine silver powder having simultaneously excellent dispersibility (low cohesion) as intended by the present invention and a large crystallite diameter. If the degree of aggregation of the silver powder obtained by the above-described manufacturing method exceeds 5.0 due to process fluctuations or the like, the degree of aggregation can be adjusted by performing the pulverization treatment. The pulverization treatment is to separate the agglomerated powder into a single powder.
[0028]
If the purpose is simply pulverization, high energy ball mill, high-speed conductor impingement airflow pulverizer, impact pulverizer, gauge mill, medium agitation mill, high water pressure Various things such as a pulverizer can be used. However, considering the reduction of the viscosity of the silver paste as much as possible, considering the reduction of the viscosity when processed into a conductive paste as described above, the specific surface area of the powder should be as small as possible. Is required. Therefore, even if granulation is possible, it should not be a granulation technique that damages the surface of the granule during granulation and increases its specific surface area.
[0029]
Based on this recognition, the present inventors determined that the two methods are effective. What is common to these two methods is to minimize the contact of silver powder particles with the inner wall of the device, stirring blades, grinding media, etc., and the agglomerated powder particles collide with each other. Moreover, it is a method capable of sufficiently pulverizing. That is, it should not damage the surface of the powder by contacting the inner wall of the apparatus, the stirring blade, the grinding medium, etc., increase the surface roughness, and deteriorate the sphericity. Then, by causing sufficient collision between powder particles, the powder particles in an agglomerated state are broken down, and at the same time, a method capable of smoothing the surface of the powder particles by collision between the powder particles is employed.
[0030]
First, the dried silver powder in an agglomerated state is pulverized using a wind circulator utilizing centrifugal force. The term “wind circulator using centrifugal force” as used herein means that air is blown and blown up in a circular orbit to circulate the agglomerated silver powder. It is used to collide with each other in an air current and perform a pulverization operation. At this time, it is also possible to use a commercially available air classifier using centrifugal force. In such a case, it is not intended only for classification, but an air classifier serves as a circulator that blows air and blows the agglomerated silver powder so as to draw a circumferential orbit.
[0031]
Second, the silver powder slurry containing the silver powder in an agglomerated state is pulverized using a fluid mill using centrifugal force. The "fluid mill using centrifugal force" here refers to the flow of silver powder slurry at a high speed so as to draw a circular orbit, and the particles aggregated by the centrifugal force generated at this time collide with each other in a solvent. And used for performing the pulverization work. By doing in this way, the silver powder slurry which the pulverization operation was completed is washed, filtered, and dried, whereby the low-aggregation silver powder whose pulverization operation has been completed is obtained.
[0032]
By using the silver powder according to the present invention obtained by the above-described production method, it is possible to produce a conductive paste having a low viscosity that has never been achieved. And the dimensional change by baking processing of the circuit drawn by using the conductive paste, the electrode shape, etc. can be minimized.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail through an embodiment while comparing with a comparative example.
[0034]
(First embodiment)
Initially, the manufacturing method of a silver chelate complex slurry is demonstrated. Here, 175 g of silver nitrate solution was dissolved in 1750 ml of pure water. On the other hand, 392 g of ethylenediaminetetraacetate was dissolved in 5250 ml of pure water. The silver nitrate solution and the ethylenediaminetetraacetate solution were mixed and stirred to obtain a silver chelate complex slurry. The liquid temperature at this time is room temperature.
[0035]
The silver chelate complex slurry was filtered, and the silver chelate complex was once collected by filtration and washed with 350 ml of pure water. This is because the solution at the time of producing the silver chelate complex slurry is not used in the following reduction step. When the pure water washing was completed, 7000 ml of pure water was added to the silver chelate complex to form a reslurry.
[0036]
Next, a solution in which 200 g of potassium sulfite was dissolved in 1750 ml of pure water was added to the reslurry, and the solution temperature was maintained at 50 ° C., followed by reduction for 30 minutes to obtain fine silver powder. Thereafter, the produced fine silver powder was collected by filtration, washed with 350 ml of pure water and 175 ml of methanol, and dried to obtain a fine silver powder.
[0037]
Here silver powder average particle diameter _{D 50} of the laser diffraction scattering particle size distribution measurement method obtained is 2.78Myuemu, the average particle diameter _{D IA} obtained by image analysis 0.60, _therefore, D 50 _{/ D IA} The degree of aggregation calculated in (4) was 4.63. The average particle diameter _{D 50} of the laser diffraction scattering particle size distribution measuring method in the present specification, the silver powder 0.1g was mixed with 0.1% aqueous solution of SN Dispersant 5468 (manufactured by San Nopco Limited), ultrasonic homogenizer (Nippon Seiki After being dispersed for 5 minutes using a US-300T (manufactured by Seisakusho Co., Ltd.), the measurement was performed using a Micro Trac HRA 9320-X100 type (Leeds + Northrup), which is a laser diffraction / scattering particle size distribution measuring device.
[0038]
Further, when the crystallite diameter is measured, the crystallite diameter of the fine silver powder of this embodiment is 40.9 nm, and the crystallite diameter is larger than the crystallite diameter of the silver powder produced by the atomization method. Was confirmed.
[0039]
Next, an epoxy conductive paste was produced using fine silver powder. 85 parts by weight of the obtained fine silver powder, 3 parts by weight of Epicoat 828 made by Yuka Shell Co., Ltd. for the first epoxy resin, and 9 parts by weight of YD-171 made by Toto Kasei Co., Ltd. for the second epoxy resin As an epoxy resin curing agent, 3 parts by weight of Amicure MY-24 manufactured by Ajinomoto Co., Inc. was mixed and kneaded for 30 minutes to obtain an epoxy-based conductive paste. When the viscosity immediately after the production of the epoxy conductive paste obtained as described above was measured, a result of 150 Pa · s was obtained. In addition, the measurement of the viscosity in this specification uses a RE-105U which is a viscometer manufactured by Toki Sangyo Co., Ltd. and measured at a rotation speed of 0.5 rpm.
[0040]
As will be apparent from comparison with the comparative examples described below, the fine silver powder obtained by the present embodiment is fine and excellent in dispersibility, and at the same time has a large crystallite diameter. It is. In particular, the crystallite diameter exceeds 40 nm, and is an ideal fine grain in a state where the balance of the characteristics of fine grain, high dispersibility, and large crystallite diameter, which is the object of the present invention, is achieved. It is silver powder.
[0041]
(Second Embodiment)
In this embodiment, reslurry was obtained by the same process as in the first embodiment, and 330 ml of a 1 g / l concentration gelatin solution obtained by dissolving gelatin in warm water was added thereto as a dispersant.
[0042]
Then, a solution obtained by dissolving 200 g of potassium sulfite in 1750 ml of pure water is added to the reslurry to which the gelatin solution has been added, and the solution temperature is kept at 50 ° C., and the mixture is stirred for 30 minutes to reduce the fine silver powder. Obtained. Thereafter, the produced fine silver powder was collected by filtration, washed with 350 ml of pure water and 175 ml of methanol, and dried to obtain a fine silver powder.
[0043]
Here silver powder average particle diameter _{D 50} of the laser diffraction scattering particle size distribution measurement method obtained is 0.53 .mu.m, the average particle diameter _{D IA} obtained by image analysis 0.24, _therefore, D 50 _{/ D IA} The degree of aggregation calculated in (2) was 2.21.
[0044]
Moreover, when the crystallite diameter is measured, the crystallite diameter of the fine silver powder of this embodiment is 20.3 nm, and it has a large crystallite diameter equivalent to the crystallite diameter of the silver powder produced by the atomization method. It was confirmed that
[0045]
Next, an epoxy conductive paste similar to that of the first embodiment was manufactured using fine silver powder. As a result, a viscosity of 170 Pa · s was obtained when the viscosity immediately after production of the obtained epoxy conductive paste was measured.
[0046]
As will be apparent from comparison with the comparative examples described below, the fine silver powder obtained by the present embodiment is fine and excellent in dispersibility, and at the same time has a large crystallite diameter. It is. Although the crystallite size is inferior to that of the first embodiment, it can be seen that the crystallite size is particularly fine and has excellent dispersibility. Therefore, it can be seen that there is a balance between the characteristics of fine particles, high dispersibility, and large crystallite diameter, which are the objects of the present invention.
[0047]
(First comparative example)
In this comparative example, 50 g of silver nitrate was first dissolved in 600 ml of pure water. Then, 46 ml of a 25 wt% ammonia solution was added thereto. And it mixed and stirred and obtained the silver chelate complex solution. The liquid temperature at this time is room temperature.
[0048]
Next, a solution in which 26 g of glucose was dissolved in 300 ml of pure water was added to the silver chelate complex solution, and the solution temperature was maintained at 70 ° C., followed by reduction for 5 minutes to obtain silver powder. Thereafter, the produced silver powder was collected by filtration, and the silver powder was washed with 100 ml of pure water and 50 ml of methanol and dried to obtain a completed silver powder.
[0049]
Here silver powder average particle diameter _{D 50} of the laser diffraction scattering particle size distribution measurement method obtained is 6.64Myuemu, the average particle diameter _{D IA} obtained by image analysis 0.45, _therefore, D 50 _{/ D IA} The agglomeration degree calculated by (1) was 14.76, and the dispersibility of the powder particles was very poor.
[0050]
Further, when the crystallite diameter is measured, the crystallite diameter of the fine silver powder of this embodiment is 48.1 nm, and the crystallite diameter is larger than the crystallite diameter of the silver powder produced by the atomization method. Was confirmed.
[0051]
Next, an epoxy conductive paste similar to that of the first embodiment was manufactured using the obtained silver powder. As a result, when the viscosity immediately after manufacture of the obtained epoxy-based conductive paste is measured, a result of 430 Pa · s is obtained, which indicates that the viscosity is increased as compared with the above-described embodiment.
[0052]
As is clear from the comparison with the embodiment described above, the silver powder obtained by this comparative example lacks the characteristics of fine particles and excellent dispersibility, but has a very large crystallite diameter. You can see that. Therefore, it can be seen that the characteristics of the fine particles, high dispersibility, and large crystallite diameter, which are the objects of the present invention, are not balanced.
[0053]
(Second comparative example)
In this comparative example, 50 g of silver nitrate was first dissolved in 794 ml of pure water. And 200 ml of concentration 25 wt% ammonia liquid was added there. And it mixed and stirred and obtained the silver chelate complex solution. The liquid temperature at this time is room temperature.
[0054]
Next, a solution obtained by dissolving 16.5 g of hydroquinone in 1000 ml of pure water is added to the silver chelate complex solution, and the solution temperature is kept at 20 ° C., and the mixture is stirred for 3 minutes to obtain a silver powder. It was. Thereafter, the produced silver powder was collected by filtration, and the silver powder was washed with 100 ml of pure water and 50 ml of methanol and dried to obtain a completed silver powder.
[0055]
Here silver powder average particle diameter _{D 50} of the laser diffraction scattering particle size distribution measurement method obtained is 1.78Myuemu, the average particle diameter _{D IA} obtained by image analysis 0.57, _therefore, D 50 _{/ D IA} The degree of aggregation calculated in (3) is 3.12, and it can be seen that the particles are fine and the dispersibility of the particles is very high.
[0056]
However, when the crystallite size is measured, the crystallite size of the fine silver powder of the present embodiment is 7.8 nm, and the crystallite size is considerably smaller than the crystallite size of the silver powder produced by the atomization method. You can see that.
[0057]
Next, an epoxy conductive paste similar to that of the first embodiment was manufactured using the obtained silver powder. As a result, when the viscosity immediately after production of the obtained epoxy conductive paste is measured, a result of 170 Pa · s is obtained, and it can be seen that the high dispersibility keeps the viscosity low.
[0058]
As is clear from comparison with the embodiment described above, the silver powder obtained by this comparative example is excellent in the properties of being fine and excellent in dispersibility, but in order to maintain good heat shrinkage resistance. It can be seen that it does not have a large crystallite diameter. Therefore, it can be seen that the characteristics of the fine particles, high dispersibility, and large crystallite diameter, which are the objects of the present invention, are not balanced.
[0059]
【The invention's effect】
The low-cohesive silver powder according to the present invention is fine, has high dispersibility, has a large crystallite diameter for excellent heat shrinkage resistance, and has a good balance of these characteristics. Such fine silver powder has been thought to be unobtainable at all. However, if the production method according to the present invention is employed, the fine silver powder can be produced very efficiently. As a result, the circuit of the electronic device or the like, the electrode shape, and the like can be easily routed, the dimensional change during the sintering process can be minimized, and a circuit having a small dimensional change rate can be formed.

Claims (7)

A silver powder obtained by a wet reduction method, the average particle diameter D ₅₀ 0.1μm~3μm by a laser diffraction scattering particle size distribution measuring method, and was obtained by the average particle diameter D ₅₀ and the image analysis der values of cohesion degree than 5.0 represented by _D 50 _{/ D IA} with an average particle diameter _{D IA} to be is, and, low aggregation crystallite diameter, characterized in der Rukoto than 20nm Silver powder. The low cohesive silver powder according to claim 1, which is used for a conductive paste. (1) Add ethylenediaminetetraacetate to a silver nitrate solution having a concentration of 80 g / l to 120 g / l to prepare a silver chelate complex slurry of silver and ethylenediaminetetraacetate,
(2) The silver chelate complex slurry is filtered and washed to collect the silver chelate complex,
(3) Add pure water to the silver chelate complex to make a reslurry,
(4) A reducing agent is added to the silver chelate complex-containing slurry to obtain a fine silver powder by causing a slow reduction reaction,
(5) The low-aggregation silver powder according to claim 1 or 2 obtained by collecting the fine silver powder by filtration, washing and drying. A method of manufacturing a low cohesion silver powder according to claim 1 using a wet reduction method of reacting a silver chelate complex slurry with a reducing agent,
(1) Add ethylenediaminetetraacetate to a silver nitrate solution having a concentration of 80 g / l to 120 g / l to prepare a silver chelate complex slurry of silver and ethylenediaminetetraacetate,
(2) The silver chelate complex slurry is filtered and washed to collect the silver chelate complex,
(3) Add pure water to the silver chelate complex to make a reslurry,
(4) A reducing agent is added to the silver chelate complex-containing slurry, and a fine silver powder is obtained by gently causing a reduction reaction.
(5) A method for producing a low cohesive silver powder, wherein the fine silver powder is collected by filtration, washed and dried. The method for producing a low cohesive silver powder according to claim 4 , wherein a dispersant is added to the silver chelate complex-containing slurry. Reducing agents, sulfites, glucose, hydrazine, hydroquinone, formalin, ascorbic acid, hypophosphorous acid, SBH, sucrose, fructose, menthol, claim 4 or claim is a combination of one or two or more polyols Item 6. A method for producing the low-cohesive silver powder according to Item 5 . The electroconductive paste obtained using the low cohesion silver powder in any one of Claims 1 thru | or 3 .