JP2017137530A - Copper powder and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper powder having a granular shape, particle diameter of 0.1 μm to 3.0 μm, excellent in oxidation resistance and suitable for wire formation of an electronic material for use for narrowing the wire and a manufacturing method therefor.SOLUTION: The copper powder has average particle diameter of a primary particle measured by a scanning electron microscopy of 0.1 μm to 3.0 μm, relative standard deviation value of the particle diameter, which is a value of standard deviation value of the particle diameter of the primary particle divided by average particle diameter of 0.3 or less and a value of crystalline diameter divided by the average particle diameter of 0.07 or more. The copper powder can be manufactured by mixing a copper compound solution, a hydroxide solution of alkali metal and a dispersant solution to manufacture a copper salt solution and maintaining the copper salt solution and a reductant solution in a range of 50°C to 90°C and mixing them with adding the reductant solution to the copper salt solution.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a copper powder useful for forming a wiring of an electronic material and a manufacturing method thereof.

  Conventionally, metal powder has been used as a wiring forming material for electronic parts such as conductive pastes for printed wiring, semiconductor internal wiring, connection between printed wiring boards and electronic parts, and the like. In recent years, in the fields of solar cell electrodes, LEDs, and the like, demand for thinning of wiring has increased, and therefore metal powders for conductive paste that can cope with thinning are demanded.

  Conventionally, silver powder has been used as a metal powder for a conductive paste. However, since the price of silver bullion is expensive, alternatives to copper powder are being actively investigated.

  The properties required for the copper powder used in the conductive paste for fine wires vary depending on the application and use conditions. For example, the shape is granular, the particle size is small as 0.1 μm to 3.0 μm, and uniform. It is important that the oxidation resistance is high. If the particle size exceeds 3.0 μm, the wiring cannot be thinned. Further, it is known that increasing the crystallite diameter is effective for increasing the oxidation resistance.

  For example, Patent Document 1 discloses metallic copper particles having a BET diameter of 3 μm or less, a spherical shape, and a crystallite size of 0.1 μm to 10 μm. According to the method described in Patent Document 1, it is possible to produce a copper powder having a large crystallite diameter, but in observation of a scanning electron micrograph, particles of 0.3 μm to 7 μm are observed, Particles having a particle size exceeding 3 μm are mixed. As described above, since copper particles having a particle size of 0.1 μm to 3.0 μm are required as the copper powder used in the copper paste for fine wires, it is difficult to use the copper particles described in this document. Become. Furthermore, the manufacturing method described in this document is a method in which ammonia gas is blown into copper melted at 1120 ° C. or higher, and a manufacturing method suitable for industrial mass production in that a harmful gas is used at a high temperature. is not.

  Patent Document 2 includes a step of mixing a cuprous oxide powder slurry with a mixed acid of hydroxycarboxylic acid and sulfuric acid, and a step of stirring and holding the mixed solution, and mixing the cuprous oxide powder slurry and the mixed acid. Disclosed is a method for producing copper fine powder in which the time is less than 5 minutes, the average particle diameter of the obtained copper fine powder is 10 nm to 50 nm, and the ratio of the crystallite diameter to the average particle diameter is 0.5 or less. ing. However, in this manufacturing method, only copper particles having a particle size of 50 nm or less can be produced, and particles having a particle size of 50 nm or less are not easily pasted because of strong aggregation. Therefore, it becomes difficult to use the copper particles described in this document as the copper powder of the copper paste for fine wires.

  As described above, in the conventional method, copper powder having a granular shape, a particle size of 0.1 μm to 3.0 μm, uniform, and excellent in oxidation resistance is manufactured suitable for industrial mass production. Could not be produced by the method. Therefore, there is a demand for a method suitable for industrial mass production that can efficiently produce copper powder that has the above-described characteristics and that is useful for a conductive paste suitable for thinning of wiring.

JP 2004-124257 A Japanese Patent No. 4687599

  The present invention has been made in view of such a conventional situation, and has a granular shape, a uniform particle size of 0.1 μm to 3.0 μm, excellent oxidation resistance, and thinning use. An object of the present invention is to provide a copper powder and a method for producing the copper powder, which are suitable for use in forming a wiring of the electronic material.

  This inventor repeated earnest examination in order to solve the subject mentioned above. As a result, a copper salt solution containing a dispersant was prepared, the temperature of the copper salt solution and the reducing agent aqueous solution was controlled within a specific range, the reducing agent solution was added to the copper salt solution, and the temperature The present inventors have found that by causing a reduction reaction while maintaining the conditions, it is possible to obtain a copper powder having a particle size of 0.1 μm or more and 3.0 μm or less, which is uniform and has a large crystallite size, and completes the present invention. It came to.

  (1) In the first invention of the present invention, the average particle size of primary particles measured by a scanning electron microscope is 0.1 μm or more and 3.0 μm or less, and the standard deviation value of the particle size of the primary particles is A copper having a relative standard deviation value of a particle diameter, which is a value divided by the average particle diameter, of 0.3 or less, and a value obtained by dividing the crystallite diameter by the average particle diameter is 0.07 or more. It is powder.

  (2) 2nd invention of this invention is copper powder whose said crystallite diameter is 60 nm or more in 1st invention.

  (3) 3rd invention of this invention is copper powder whose shape of the said copper powder is a granular form in 1st or 2nd invention.

  (4) A fourth invention of the present invention is the copper powder according to any one of the first to third inventions, wherein the carbon content of the copper powder is 0.05% by mass or more and 0.5% by mass or less. It is.

  (5) The fifth invention of the present invention is the method according to any one of the first to fourth inventions, wherein heating is performed at a temperature increase rate of 10 ° C./min from room temperature in the atmosphere by measurement using a thermal analyzer. The copper powder has a 0.5% weight increase temperature exceeding 230 ° C.

  (6) A sixth invention of the present invention is a conductive paste obtained by kneading a copper powder, a resin, and a solvent according to any one of the first to fourth inventions.

  (7) The seventh invention of the present invention is a copper salt solution preparation in which a solution containing a copper compound, a solution containing an alkali metal hydroxide, and a solution containing a dispersant are mixed to prepare a copper salt solution. A copper particle generating step of mixing the copper salt solution and the reducing agent solution to generate copper particles, and in the copper particle generating step, the temperature of the copper salt solution and the reducing agent solution is 50 It is a manufacturing method of the copper powder characterized by mixing by adding this reducing agent solution to this copper salt solution as the range of 90 degreeC or more and 90 degrees C or less.

  (8) According to an eighth aspect of the present invention, in the seventh aspect, in the copper salt solution preparation step, the amount of the dispersant added is 0.1% by mass or more based on the amount of copper in the copper compound. It is a manufacturing method of copper powder which makes it the range of 10 mass% or less.

  (9) According to a ninth aspect of the present invention, in the seventh or eighth aspect, the dispersant is polyvinyl alcohol, polyethyleneimine, polyvinylpyrrolidone, a modified silicone oil surfactant, and a polyether surfactant. It is a manufacturing method of copper powder which is at least 1 sort chosen from.

  (10) A tenth aspect of the present invention is the method for producing copper powder according to any of the seventh to ninth aspects, wherein the copper compound is copper sulfate pentahydrate.

  (11) The eleventh invention of the present invention is the method for producing copper powder according to any of the seventh to tenth inventions, wherein the alkali metal hydroxide is sodium hydroxide.

  (12) According to a twelfth aspect of the present invention, in any one of the seventh to eleventh aspects, in the copper particle generation step, the amount of the reducing agent added is 1 with respect to the amount of copper in the copper compound. It is a manufacturing method of copper powder which makes it more than equivalent and below 7 equivalent.

  (13) The thirteenth aspect of the present invention is the copper powder manufacturing method according to any one of the seventh to twelfth aspects, wherein the reducing agent is ascorbic acid.

  (14) In a fourteenth aspect of the present invention, in any one of the seventh to thirteenth aspects, the copper powder is obtained by observing the crystallite diameter of the copper powder with a scanning electron microscope. It is the manufacturing method of copper powder whose value divided by the average particle diameter of the primary particle to be measured is 0.07 or more.

  (15) The fifteenth aspect of the present invention is the copper powder manufacturing method according to the fourteenth aspect, wherein the copper powder has a crystallite diameter of 60 nm or more.

  (16) In a fourteenth aspect of the present invention, in the fourteenth or fifteenth aspect, the copper powder is a value obtained by dividing a standard deviation value of a particle diameter of primary particles of the copper powder by the average particle diameter. This is a copper powder manufacturing method in which the relative standard deviation value of a certain particle size is 0.3 or less.

  (17) The seventeenth invention of the present invention is the copper powder according to any one of the fourteenth to sixteenth inventions, wherein the copper powder has a carbon content of 0.05% by mass or more and 0.5% by mass or less. It is a manufacturing method.

  (18) An eighteenth aspect of the present invention is a method for producing a conductive paste, which is produced by kneading a copper powder, a resin, and a solvent according to any one of the first to fifth aspects of the invention.

  According to the present invention, the shape is granular, the particle size is 0.1 μm to 3.0 μm, uniform, excellent in oxidation resistance, and suitable for use in forming wiring for electronic materials for thinning applications. , Copper powder and a method for producing the copper powder can be provided. In addition, according to the method for producing copper powder according to the present invention, copper powder can be efficiently produced in an aqueous solution system that is easy to handle and suitable for industrial mass production, and its industrial value is extremely high. large.

2 is a SEM observation photograph of the copper powder obtained in Example 1. FIG. 4 is a SEM observation photograph of the copper powder obtained in Example 2. FIG. 4 is a SEM observation photograph of the copper powder obtained in Comparative Example 1. FIG.

  Hereinafter, specific embodiments of the present invention (hereinafter referred to as “present embodiments”) will be described in detail. However, the present invention is not limited to the following embodiments and does not depart from the gist of the present invention. As long as it can be changed as appropriate. In this specification, “X to Y” (X and Y are arbitrary numerical values) means “X or more and Y or less”.

<< 1. Copper powder >>
In the copper powder according to the present embodiment, the average particle size of primary particles measured by a scanning electron microscope (SEM) is 0.1 μm or more and 3.0 μm or less, and the standard deviation value of the particle size of primary particles is averaged. The relative standard deviation value of the particle diameter, which is a value divided by the particle diameter, is 0.3 or less, and the value obtained by dividing the crystallite diameter by the average particle diameter is 0.07 or more.

  More specifically, the copper powder has a granular shape, and the average particle size is in the range of 0.1 μm to 3.0 μm, more preferably in the range of 0.3 μm to 2.5 μm. is there. By using the copper powder having an average particle diameter in such a range, a conductive (copper) paste suitable for forming a thinned wiring can be obtained.

  Here, an average particle diameter is an average value calculated | required from the particle size of the primary particle measured by observing a certain number of copper powder by SEM and observing. The primary particles refer to those considered as unit particles from the SEM observation image, and do not mean so-called secondary particles formed by aggregation and bonding of the unit particles.

  When the average particle size of the copper powder is less than 0.1 μm, the particles are likely to aggregate and difficult to form a paste. On the other hand, when the average particle size exceeds 3.0 μm, it is difficult to narrow the line width when the wiring is formed by the paste containing the copper powder, and it is difficult to make the wiring thin.

  In addition, the copper powder has a relative standard deviation value of 0.3 or less, which is a value obtained by dividing the standard deviation value of the primary particle diameter by the average particle diameter measured by the SEM described above. If the relative standard deviation of this particle size exceeds 0.3, copper particles will not be uniformly present in the printed film, resulting in non-uniform thickness and thickness of the wiring and electrodes, as well as curing. Or since baking becomes non-uniform | heterogenous, the resistance of an electrically conductive film becomes large, or an electrically conductive film tends to become weak and weak.

  Moreover, this copper powder has a value (crystallite diameter / average particle diameter) of 0.07 or more obtained by dividing the crystallite diameter by the average particle diameter measured by the SEM described above. The crystallite diameter can be calculated from the X-ray diffraction result using the Scherrer method. The higher the index represented by the crystallite diameter / average particle diameter, the smaller the number of crystal grains constituting the copper powder, that is, the higher the crystallinity. As described above, when the crystallite diameter / average particle diameter is a copper powder having a high crystallinity of 0.07 or more, the crystal grain boundary is reduced and it is difficult to oxidize.

  Here, the crystallite diameter of the copper powder according to the present embodiment is 60 nm or more, preferably 130 nm or more. The upper limit value of the crystallite diameter is not particularly limited, but is preferably 900 nm or less.

  Further, the upper limit of the crystallite diameter / average particle diameter is not particularly limited, but is preferably 0.3 or less. The crystallite diameter / average particle diameter is more preferably 0.08 or more and 0.3 or less, and particularly preferably 0.1 or more and 0.2 or less.

  Further, the copper powder according to the present embodiment preferably has a carbon content of 0.05% by mass or more and 0.5% by mass or less, and preferably 0.1% by mass or more and 0.4% by mass or less. More preferred. Carbon content shows the adhesion amount of the organic substance derived from the dispersing agent etc. in the copper powder surface. As will be described later, in the present embodiment, when the copper particles are generated, a dispersant is used as one of the purposes to suppress aggregation of the generated copper particles, but the obtained copper powder also has a surface thereof. By attaching an appropriate amount of the dispersant, aggregation can be suppressed, and dispersibility when the copper powder is used as a conductive paste can be enhanced.

  If the carbon content of the copper powder is less than 0.05% by mass, a sufficient aggregation suppressing effect cannot be obtained, and the desired dispersibility may not be obtained when a conductive paste is obtained. On the other hand, when the carbon content increases, the aggregation suppressing effect and the dispersibility improving effect increase, but the organic matter attached to the surface of the copper powder inhibits the sintering of the copper powder when the conductive paste is heat-cured. It becomes a factor to do. From this, when carbon content exceeds 0.5 mass%, sinterability may fall.

  Moreover, the copper powder which concerns on this Embodiment is excellent in oxidation resistance, and is suitable as a copper powder used for the electrically conductive paste for thin wires. Specifically, the oxidation resistance can be quantitatively evaluated by, for example, “0.5% weight increase temperature” by measurement using a thermal analyzer, and the copper powder is preferably in the air. In this case, the 0.5% weight increase temperature exceeds 230 ° C. when heated from room temperature at a heating rate of 10 ° C./min.

≪2. Manufacturing method of copper powder >>
Next, the manufacturing method of the copper powder which has the characteristic structure mentioned above is demonstrated.

  The copper powder which concerns on this Embodiment has the process of producing a copper salt solution, and the process of producing the copper particle by mixing the produced copper salt solution and a reducing agent solution. And in this manufacturing method, while adjusting and maintaining the copper salt solution and the reducing agent solution in a specific temperature range, the reducing agent solution is added to the copper salt solution to produce copper particles. It is a feature.

  Here, the conventional method for producing copper powder has a problem that it is impossible to produce copper powder having a granular shape, a small and uniform particle size, and a large crystallite size by a method suitable for industrial production. . However, according to the inventor's research, a copper salt solution containing a dispersant is prepared, the temperature of the copper salt solution and the reducing agent aqueous solution is adjusted to a specific range, and the copper salt solution as a raw material is reduced. It was found that a copper powder having a granular shape, a small particle diameter, and a large crystallite diameter can be obtained by adding an agent solution and causing a reduction reaction while maintaining the temperature condition.

  More specifically, the temperature of the copper salt solution and the reducing agent solution is adjusted to the range of 50 ° C. or higher and 90 ° C. or lower, and the copper salt solution is added to the copper salt solution while maintaining the temperature. Is generated. According to such a manufacturing method, a copper powder that is a granular shape, a small and uniform particle diameter, and a large crystallite diameter, which is useful for a conductive paste suitable for thinning a wiring, It can be manufactured industrially.

  Hereinafter, the method for producing copper powder according to the present embodiment will be described more specifically. In the following description, the liquid after the copper salt solution and the reducing agent solution are mixed is also referred to as “reaction liquid”.

(1) Production of copper salt solution In this method for producing copper powder, first, a copper salt solution, which is a raw material solution for producing copper particles, is produced. Specifically, a solution containing a copper compound, a solution containing an alkali metal hydroxide, and a solution containing a dispersant are mixed to prepare a copper salt solution.

(Copper compound solution)
With respect to the solution containing the copper compound, the copper compound as a starting material is not particularly limited, and various copper compounds can be used, but among them, it is cheaper and more pure than other copper compounds. It is preferable to use copper sulfate pentahydrate because it is easily available.

  Moreover, it is although it does not specifically limit as a density | concentration of a copper compound, It is preferable to make it become the range of 100 g / L-2000 g / L as copper concentration in the obtained copper salt solution. Even if the concentration of copper is low, particle growth occurs and copper particles can be obtained. However, if the copper concentration is less than 100 g / L in the copper salt solution, productivity cannot be increased. In addition, the amount of drainage increases and the cost increases. On the other hand, when the concentration of copper exceeds 2000 g / L, it is close to solubility in water and may not be sufficiently dissolved.

(Alkali metal hydroxide solution)
With respect to a solution containing an alkali metal hydroxide, various hydroxides can be used as the alkali metal hydroxide. Among them, sodium hydroxide and potassium hydroxide are preferably used, It is more preferable to use sodium oxide. These alkali metal hydroxides are readily available and are less expensive than other hydroxides.

  The concentration of the alkali metal hydroxide is such that the copper salt has a pH at which the reduction reaction of the reducing agent proceeds sufficiently in the reaction solution after adding the reducing agent solution described later to the copper salt solution. It is preferable to adjust the concentration in the solution. Specifically, for example, when ascorbic acid is used as the reducing agent, it is preferable that the pH of the reaction solution is 3.0 or more. If the pH of the reaction solution is less than 3.0, the reduction reaction with ascorbic acid that is a reducing agent may not easily proceed.

  When the pH of the reaction solution is increased, copper hydroxide is formed in the reaction solution, and copper particles are generated by the reduction reaction from the copper hydroxide. The reaction in which copper particles are produced from copper hydroxide has a lower rate than the reaction in which copper particles are produced from copper ions, so that crystals grow gradually, resulting in highly crystalline copper particles. It becomes easy. For this reason, it is more preferable that the pH of the reaction solution is 4.0 or more.

(Dispersant solution)
In the method for producing a copper powder according to the present embodiment, when producing a copper salt solution, an aqueous solution of a dispersant is mixed so that copper particles generated by a reduction reaction with a reducing agent do not aggregate. In addition, the dispersant has an effect of slowing down the reduction reaction as the concentration in the reaction solution increases. From this, by making a copper salt solution contain a dispersing agent, the reaction rate of a reductive reaction can be reduced and a highly crystalline copper particle can be obtained.

  Here, it is important to obtain a copper powder having a small crystal grain boundary and a large crystallite diameter. For this purpose, the crystal grain boundary is given priority by the growth of each crystal of the copper particle due to the high crystallinity. It is preferable to set the conditions to be less. From such a point, it is preferable to control the rate of the reduction reaction, and it is preferable to control the concentration of the dispersant in the reaction solution to be within an appropriate range.

  Specifically, the concentration of the dispersant is preferably 0.1% by mass or more and 10% by mass or less, and 0.3% by mass or more and 7% by mass with respect to the copper amount of the copper compound in the reaction solution. % Or less, more preferably 0.5% by mass or more and 5% by mass or less. When the concentration of the dispersing agent is less than 0.1% by mass in the reaction solution, the rate of the reduction reaction is increased, and a highly crystalline copper powder may not be obtained. On the other hand, if the concentration of the dispersant exceeds 10% by mass in the reaction solution, the rate of the reduction reaction is too low, the productivity is deteriorated, and in some cases, the reduction reaction may not proceed.

  The dispersant is not particularly limited and may be, for example, at least one selected from polyvinyl alcohol, polyethyleneimine, polyvinylpyrrolidone, modified silicone oil surfactants, polyether surfactants, and the like. preferable. Two or more of these dispersants may be used in combination.

(2) Production of copper particles by addition of reducing agent Next, the produced copper salt solution and the reducing agent solution are mixed to produce copper particles. At this time, in the method for producing copper powder according to the present embodiment, the temperatures of the copper salt solution and the reducing agent solution are controlled within a specific range, and the reducing agent solution is added to the copper salt solution that is the raw material solution. To go.

(Reducing agent solution)
Although it does not specifically limit as a reducing agent, It is preferable to use the compound with comparatively weak reducing power, for example, it is preferable to use the organic compound which has ascorbic acid or its lactone structure similar to it. Ascorbic acid has a slow reducing action, and by using an organic compound having such a lactone structure, highly crystalline copper particles can be efficiently generated.

  In this method for producing copper powder, the solution containing the reducing agent described above is added to the copper salt solution. The amount of the reducing agent added is 1 in the reaction solution relative to the copper amount of the copper compound. It is preferable to set the amount corresponding to an equivalent amount or more and 7 equivalents or less. When the amount of the reducing agent added is less than 1 equivalent with respect to the copper amount of the copper compound, an unreduced copper salt may remain, whereas when it exceeds 7 equivalents, the production cost increases.

  Here, in the method for producing copper powder according to the present embodiment, it is important to add a reducing agent solution to a copper salt solution that is a raw material solution, thereby achieving high crystallinity of copper particles. Can be generated automatically.

  Moreover, when adding a reducing agent solution with respect to a copper salt solution, the temperature of the copper salt solution and a reducing agent solution is controlled to a specific range. Specifically, the range is from 50 ° C. to 90 ° C. Moreover, it is preferable to set it as the range of 60 degreeC or more and 80 degrees C or less. By controlling the temperature of the copper salt solution and the reducing agent solution in such a temperature range and maintaining this temperature range to cause a reduction reaction, copper particles having high crystallinity can be generated. When the reaction temperature is less than 50 ° C., the crystallinity of the copper particles is lowered. On the other hand, when the reaction temperature exceeds 90 ° C., the reaction rate increases and the particle size tends to become non-uniform.

  Moreover, the retention time of the reaction solution after adding the reducing agent solution to the copper salt solution is not particularly limited, but is preferably 1 hour or longer. If the retention time of the reaction solution is less than 1 hour, the reduction reaction may not be completed, and an unreduced copper salt may remain. On the other hand, the upper limit of the retention time of the reaction solution is not particularly limited, but it should be, for example, within 5 hours from the viewpoint that the reduction reaction with a reducing agent having a relatively low reducing power such as ascorbic acid is completely completed. Is preferred. The holding time of the reaction solution is more preferably 1 hour or more and 4 hours or less, and particularly preferably 2 hours or more and 3 hours or less.

  If necessary, additives such as a pH adjuster, a complexing agent, and an antifoaming agent can be appropriately added to the reaction solution. What is necessary is just to adjust suitably the addition amount of these additives according to the objective.

(3) Filtration, washing and drying When a copper particle slurry containing copper particles is produced as described above, the slurry is filtered to separate the copper powder, washing and drying.

  The cleaning method is not particularly limited, but, for example, a method in which copper particles are put into water, stirred using a stirrer or an ultrasonic cleaner, and then collected by filtration with a suction filter or a filter press. Can be performed. Moreover, in the washing | cleaning method, it is preferable to repeat the operation which consists of throwing into water, stirring washing | cleaning, and filtration several times. In addition, as cleaning water, it is preferable to use water which does not contain an impurity element harmful to copper powder, particularly pure water.

  Further, in order to prevent aggregation of the copper powder and the like, a surface treatment agent may be added to the washing water or the like in the washing treatment, and the copper powder may be surface treated during the washing. For example, a surface treatment with a carboxylic acid solution can be added during the cleaning treatment. In addition, when such surface treatment is performed, it is preferable to perform washing | cleaning and filtration after that and to remove an excess surface treating agent.

  Next, in the drying treatment for the washed copper powder, the drying method is not particularly limited. For example, the washed copper particles are placed on a stainless steel bat, and a commercially available drying apparatus such as an atmospheric oven or a vacuum dryer is used. And can be performed by heating at a temperature of about 40 ° C. to 80 ° C.

  As described above in detail, according to the method for producing copper powder according to the present embodiment, it is possible to produce a highly crystalline copper powder that is granular, has a small particle size, is uniform, and has a large crystallite size. it can.

≪3. Conductive paste >>
As described above, the copper powder according to the present embodiment has an average particle size of primary particles measured by SEM of 0.1 μm or more and 3.0 μm or less, and the standard deviation value of the particle size of primary particles is the average particle size. The relative standard deviation value of the particle diameter, which is a value divided by the diameter, is 0.3 or less, and the value obtained by dividing the crystallite diameter by the average particle diameter is 0.07 or more. According to such a copper powder, it can be suitably used as a raw material for a conductive paste suitable for thinning wiring while suppressing aggregation.

  The conductive paste can be manufactured by mixing and kneading the above-described copper powder, binder resin, and solvent. Moreover, in order to improve the electroconductivity after hardening as needed, additives, such as antioxidant and a coupling agent, can also be mix | blended.

  Specifically, the binder resin is not particularly limited, but an epoxy resin, a phenol resin, an ethyl cellulose resin, or the like can be used. Moreover, as a solvent, organic solvents, such as ethylene glycol, diethylene glycol, triethylene glycol, glycerol, and terpineol, can be used. The amount of the organic solvent added is not particularly limited, but can be adjusted in consideration of the average particle size of the copper powder so as to have a viscosity suitable for a conductive film forming method such as screen printing or dispenser. .

  Moreover, it does not specifically limit as antioxidant which is an additive, For example, a hydroxycarboxylic acid etc. can be mentioned. More specifically, hydroxycarboxylic acids such as citric acid, malic acid, tartaric acid, and lactic acid are preferable, and citric acid or malic acid having a high adsorptive power to copper is particularly preferable. In addition, as the additive, a coupling agent, a viscosity modifier, a dispersant, a flame retardant, an anti-settling agent, and the like can be used.

  When producing the conductive paste, it can be produced by a method similar to the conventional method as long as the above-described constituent components can be uniformly dispersed. For example, each component described above can be produced by uniformly kneading using a three-roll mill or the like.

  The timing of adding the additive is not particularly limited, and may be added to the solvent simultaneously with the copper powder and the binder resin and kneaded, or the copper powder and the binder resin are mixed in the solvent and kneaded, Then, you may add using a self-revolving mixer.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Evaluation method>
For the copper powders obtained in the following examples and comparative examples, the average particle size, crystallite system, observation of shape, 0.5% weight increase temperature, and carbon content were measured by the following methods.

(Average particle size)
About the average particle diameter of the obtained copper powder, it observes using a scanning electron microscope (SEM, the JEOL Co., Ltd. make, JSM-7100F), and measures the particle size of 300 or more primary particles of copper powder. Thus, the average value was obtained to obtain the average particle size.

(Crystallite diameter)
The crystallite diameter of the obtained copper powder is measured using an X-ray diffractometer (manufactured by PAN artificial, X'pert PRO), and from the obtained X-ray diffraction pattern, it is generally known as Scherrer's formula It calculated using the method of.

(0.5% weight increase temperature)
About the 0.5% weight increase temperature of the obtained copper powder, when using a thermal analyzer (manufactured by Bruker, TG-DTA2000SR), the air flow rate was 100 mL / min, and the temperature was increased at 10 ° C./min. The weight increase amount was measured, and the temperature at which 0.5% weight increased was determined as the 0.5% weight increase temperature.

(Carbon content)
About the carbon content of the obtained copper powder, it measured by the high frequency combustion-infrared absorption method using the carbon sulfur analyzer (the product made by LECO, CS-600).

[Example 1]
500 g of copper sulfate pentahydrate (manufactured by Sumitomo Metal Mining Co., Ltd.) is dissolved in 3 L of pure water, to which 600 mL of 25% aqueous sodium hydroxide solution (manufactured by Kanto Chemical Co., Ltd.) and polyvinyl alcohol (stock) A dispersant solution prepared by dissolving 1.28 g of PVA205 (manufactured by Kuraray Co., Ltd.) in 1 L of pure water was added. Further, an antifoaming agent (manufactured by Adeka Co., Ltd., Adecanol LG-126) was diluted 100 times by volume, and 10 mL of this antifoaming agent dilution was added. Thereby, a copper salt solution was prepared.

  Next, while maintaining the prepared copper salt solution at 60 ° C. while stirring, a reducing agent solution obtained by dissolving 881 g of ascorbic acid (manufactured by Wako Pure Chemical Industries, Ltd.) in 2 L of pure water and heating to 60 ° C. The mixture was added and held at 60 ° C. with stirring for 3 hours.

  After completion of the stirring, the reaction solution was filtered using a suction filter, and the copper particles in the reaction solution were separated into solid and liquid. Subsequently, the recovered copper particles are put into 2 L of pure water, and 2.5 g of stearic acid emulsion (manufactured by Chukyo Yushi Co., Ltd., Cellosol 920) is added thereto and stirred for 15 minutes, followed by filtration with a suction filter. And recovered. Subsequently, the recovered copper particles were put into 2 L of pure water, and an operation including washing by stirring for 15 minutes and filtration by a suction filter was performed. Thereafter, the copper particles were transferred onto a stainless bat and dried at 60 ° C. for 10 hours with a vacuum dryer to obtain copper powder.

  FIG. 1 is a SEM observation photograph of the copper powder obtained in Example 1. As can be seen from the SEM photograph in FIG. 1, the obtained copper powder was in a granular shape.

  The average particle size obtained by measuring the particle size of 300 or more primary particles from the SEM image and averaging them by the number of particles was 1.86 μm, and the standard deviation value of the particle size of the primary particles was averaged. The relative standard deviation value of the particle size divided by the particle size was 0.19. The crystallite diameter was 153 nm, and the value represented by crystallite diameter / average particle diameter was 0.08.

  Furthermore, the 0.5% weight increase temperature of the obtained copper powder was 242 ° C. and exceeded 230 ° C., and the oxidation resistance was good. Moreover, the carbon content of the obtained copper powder was 0.23% by mass.

[Example 2]
25.0 g of copper sulfate pentahydrate (manufactured by Sumitomo Metal Mining Co., Ltd.) is dissolved in 150 mL of pure water, and 30 mL of 25% sodium hydroxide aqueous solution (manufactured by Kanto Chemical Co., Ltd.) and polyvinyl alcohol as a dispersant are added thereto. A dispersant solution in which 0.06 g (manufactured by Kuraray Co., Ltd., PVA205) was dissolved in 50 mL of pure water was added. Furthermore, an antifoaming agent (manufactured by Adeka Co., Ltd., Adecanol LG-126) was diluted 100 times by volume, and 5 mL of this antifoaming agent dilution was added. Thereby, a copper salt solution was prepared.

  Next, the prepared copper salt solution is kept at 80 ° C. while stirring, and 44 g of ascorbic acid (manufactured by Wako Pure Chemical Industries, Ltd.) is dissolved in 100 mL of pure water and heated to 80 ° C. The mixture was added and held at 80 ° C. with stirring for 3 hours.

  After completion of the stirring, the reaction solution was filtered using a suction filter, and the copper particles in the reaction solution were separated into solid and liquid. Subsequently, the recovered copper particles are put into 200 mL of pure water, and 0.13 g of stearic acid emulsion (manufactured by Chukyo Yushi Co., Ltd., Cellosol 920) is added thereto and stirred for 15 minutes, followed by filtration with a suction filter. And recovered. Subsequently, the recovered copper particles were put into 200 mL of pure water, and an operation consisting of washing with stirring for 15 minutes and filtration with a suction filter was performed. Thereafter, the copper particles were transferred onto a stainless bat and dried at 60 ° C. for 10 hours with a vacuum dryer to obtain copper powder.

  FIG. 2 is a SEM observation photograph of the copper powder obtained in Example 2. As can be seen from the SEM photograph in FIG. 2, the obtained copper powder was in a granular shape.

  Further, the average particle size obtained by measuring the particle size of 300 or more primary particles from the SEM image and averaging them by the number of particles is 2.38 μm, and the standard deviation value of the particle size of the primary particles is averaged. The relative standard deviation value of the particle size divided by the particle size was 0.23. The crystallite diameter was 291 nm, and the value represented by crystallite diameter / average particle diameter was 0.12.

  Furthermore, the 0.5% weight increase temperature of the obtained copper powder was 287 ° C, exceeding 230 ° C, and the oxidation resistance was good. Moreover, the carbon content of the obtained copper powder was 0.22 mass%.

[Comparative Example 1]
Copper powder was produced in the same manner as in Example 2 except that the temperature of the copper salt solution, the reducing agent aqueous solution, and the reaction solution during the holding time was 40 ° C., respectively.

  FIG. 3 is a SEM observation photograph of the copper powder obtained in Comparative Example 1. As can be seen from the SEM photograph in FIG. 3, the obtained copper powder was in a granular shape.

  Further, the average particle size obtained by measuring the particle size of 300 or more primary particles from the SEM image and averaging them by the number of particles was 1.81 μm, and the standard deviation value of the particle size of the primary particles was averaged. The relative standard deviation value of the particle size divided by the particle size was 0.29. The crystallite diameter was 97 nm, and the value represented by crystallite diameter / average particle diameter was 0.05.

  Furthermore, the 0.5% weight increase temperature of the obtained copper powder was 212 ° C., which was inferior in oxidation resistance. Moreover, the carbon content of the obtained copper powder was 0.25 mass%.

Claims (18)

The average particle size of primary particles measured by a scanning electron microscope is 0.1 μm or more and 3.0 μm or less,
The standard deviation value of the particle size of the primary particles divided by the average particle size is a relative standard deviation value of the particle size of 0.3 or less,
A value obtained by dividing the crystallite diameter by the average particle diameter is 0.07 or more. The copper powder according to claim 1, wherein the crystallite diameter is 60 nm or more. The copper powder according to claim 1 or 2, wherein the shape of the copper powder is granular. The copper powder according to any one of claims 1 to 3, wherein a carbon content of the copper powder is 0.05% by mass or more and 0.5% by mass or less. 5. The weight increase temperature of 0.5% when heated at a rate of temperature increase of 10 ° C./min from room temperature in the atmosphere, measured by a thermal analyzer, exceeds 230 ° C. 5. The copper powder as described. A conductive paste obtained by kneading the copper powder according to claim 1, a resin, and a solvent. A copper salt solution preparation step of preparing a copper salt solution by mixing a solution containing a copper compound, a solution containing an alkali metal hydroxide, and a solution containing a dispersant;
A copper particle production step of producing a copper particle by mixing the copper salt solution and the reducing agent solution,
In the copper particle generation step, the temperature of the copper salt solution and the reducing agent solution is set in a range of 50 ° C. or more and 90 ° C. or less, and mixing is performed by adding the reducing agent solution to the copper salt solution. A method for producing copper powder. In the said copper salt solution preparation process, the addition amount of the said dispersing agent shall be the range of 0.01 mass% or more and 10 mass% or less with respect to the amount of copper in the said copper compound. Method. The said dispersing agent is at least 1 sort (s) selected from polyvinyl alcohol, polyethyleneimine, polyvinylpyrrolidone, a modified silicone oil-type surfactant, and a polyether-type surfactant, The manufacture of the copper powder of Claim 7 or 8 Method. The method for producing copper powder according to any one of claims 7 to 9, wherein the copper compound is copper sulfate pentahydrate. The method for producing copper powder according to any one of claims 7 to 10, wherein the alkali metal hydroxide is sodium hydroxide. In the said copper particle production | generation process, the addition amount of the said reducing agent shall be 1 equivalent or more and 7 equivalent or less with respect to the copper amount in the said copper compound. Manufacture of the copper powder of any one of Claims 7 thru | or 11 Method. The method for producing copper powder according to any one of claims 7 to 12, wherein the reducing agent is ascorbic acid. The copper powder has a value obtained by dividing the crystallite diameter of the copper powder by the average particle diameter of primary particles measured by observing the copper powder with a scanning electron microscope. 14. The method for producing copper powder according to any one of 13 above. The method for producing copper powder according to claim 14, wherein the copper powder has a crystallite diameter of 60 nm or more. The copper powder has a relative standard deviation value of 0.3 or less, which is a value obtained by dividing the standard deviation value of the primary particle diameter of the copper powder by the average particle diameter. 15. The method for producing copper powder according to 15. The method for producing a copper powder according to any one of claims 14 to 16, wherein the copper powder has a carbon content of 0.05 mass% or more and 0.5 mass% or less. The manufacturing method of the electrically conductive paste manufactured by knead | mixing the copper powder in any one of Claims 1 thru | or 5, resin, and a solvent.