JP2015096637A - Copper-containing fine-particle aggregate and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper containing fine-particle aggregate which has low sintering temperature, suppresses viscosity rise of a paste and allows increase of the wiring density.SOLUTION: A copper-containing fine-particle aggregate contains copper and is formed by aggregation of a plurality of fine particles of particle sizes of 10-600 nm. The fine-particle aggregate has a thermal shrinkage initiation temperature in an atmosphere of 1% hydrogen-99% nitrogen of 80-300°C and particle sizes of 1.0-10.0 μm. The fine-particle preferably contains an organic polymer material further and no surface treatment agent consisting of an organic acid.

Description

  The present invention relates to an aggregate of a plurality of fine particles containing copper. The present invention also relates to a method for producing the aggregate.

  Polyester resins such as polyethylene terephthalate and polyethylene naphthalate are used as materials for flexible substrates. When wiring for an electronic circuit is formed on a flexible substrate, it is necessary to use a metal material having a sintering temperature of 300 ° C. or lower due to restrictions on the melting point of the resin. For example, silver particles are used as such a metal material. However, since silver is an expensive metal, it has been proposed to use copper, which is a metal cheaper than silver (see Patent Documents 1 to 4).

  However, the copper particles currently used have a particle size of about several μm, and as a result, the sintering temperature is relatively high at about 500 to 700 ° C. In order to lower the sintering temperature, it is effective to reduce the particle size and make it nano. However, nanoparticles are not easy to increase the wiring density due to the small size of the particles. In addition, when a wiring is formed using a conductive paste containing nanoparticles, the viscosity of the paste increases due to the small particle size, which makes it difficult to perform high-speed printing of the paste. Furthermore, nanoparticles have a problem of safety (so-called nano risk).

JP 2007-254846 A JP 2013-47365 A JP 2003-342621 A JP 2009-74152 A

  The subject of this invention is providing the copper containing particle | grains which can eliminate the various fault which the prior art mentioned above has.

  As a result of intensive studies by the inventor to solve the above-mentioned problems, an aggregate formed by assembling a plurality of copper-containing nanoparticles exhibits low-temperature sinterability of the nanoparticles and increases the viscosity of the paste. It was found that the wiring density can be further increased.

The present invention has been made based on the above findings, and is a copper-containing fine particle aggregate formed by aggregating a plurality of fine particles containing copper and having a particle size of 10 nm to 600 nm,
Provided is a copper-containing fine particle aggregate having a heat shrinkage start temperature of 80 ° C. or more and 300 ° C. or less and a particle size of 1.0 μm or more and 10.0 μm or less in a 1 vol% hydrogen-99 vol% nitrogen atmosphere. .

  In addition, the present invention provides a method for producing a copper-containing fine particle aggregate comprising a step of subjecting a plurality of fine particles containing copper and having a particle diameter of 10 nm to 600 nm to a spray drying method to collect the fine particles. To do.

  ADVANTAGE OF THE INVENTION According to this invention, the sintering temperature is low, the viscosity increase of a paste can be suppressed, and also the copper containing fine particle aggregate which can make a wiring density high, and its suitable manufacturing method are provided.

FIG. 1 is a scanning electron microscope image showing copper fine particles used in Examples and Comparative Examples. FIG. 2 is a scanning electron microscope image showing the fine particle aggregate obtained in Example 1. FIG. 3 is a scanning electron microscope image showing the fine particle aggregate obtained in Example 2. FIG. 4 is a scanning electron microscope image showing the copper fine particles of Comparative Example 1. FIG. 5 is a graph showing the results of thermomechanical analysis for the examples and comparative examples.

  Hereinafter, the present invention will be described based on preferred embodiments thereof. The copper-containing fine particle aggregate of the present invention (hereinafter, also simply referred to as “fine particle aggregate” for the sake of simplicity) is in the form of a particle in which a plurality of fine particles are aggregated. These fine particles contain copper. Examples of the fine particles containing copper include (a) fine particles made of copper, (b) fine particles made of cuprous oxide, (c) fine particles in which the surface of core material particles made of copper is coated with a metal other than copper, D) Fine particles made of a copper-based alloy. These fine particles (a) to (d) may be used alone or in combination of two or more. When the fine particles (c) are used, examples of the metal that covers the surface of the core particles made of copper include silver, tin, nickel, platinum, gold, palladium, and cobalt. In particular, it is preferable to use silver as the covering metal because of its low resistance. In the case of using the fine particles (d), examples of the alloy component of the copper-based alloy include those similar to the coating metal used for the fine particles (c). In addition, when using the fine particles of (A), depending on the storage state, a trace amount of copper oxide may inevitably exist on the surface of the fine particles made of copper, but such a state is present. Such cases are also included in the “fine particles of copper” that can be used in the present invention.

  The fine particles constituting the fine particle aggregate of the present invention have an advantageous particle size of 10 nm or more and 600 nm or less. When the particle diameter of the fine particles is less than 10 nm, the volume shrinkage rate during sintering may become extremely large. On the other hand, when the particle diameter exceeds 600, it may not be easy to sufficiently lower the heat shrinkage starting temperature of the fine particle aggregate of the present invention. Further, it is not easy to increase the wiring density of the electronic circuit. From these viewpoints, the particle diameter of the fine particles is preferably 50 nm or more and 500 nm or less. The particle size of the fine particles can be measured as individual particles after pulverizing the fine particle aggregate of the present invention by the following method. That is, 0.1 kg of the fine particle aggregate of the present invention is placed in 0.1 kg of methanol as a dispersion medium and stirred well to produce a slurry having a fine particle aggregate concentration of 50 mass%. Subsequently, the obtained slurry is pulverized using a medium mill. Specifically, 0.4 kg of zirconia beads having a diameter of 0.1 mm were prepared, and [dispersion in slurry (mass%)]: [media beads (mass%)] = 1: 2 was set. Fill the mat. Thereafter, the rotation speed is set to 1000 rpm and the slurry is circulated for 10 minutes to perform the crushing treatment. Thereafter, the individual particles are observed by SEM, and the particle size is measured by image processing such as MAC-View (Mountech Co., Ltd.). The particle diameter is a circle-equivalent diameter derived from the area in plan view, and primary particles can be reliably captured. The measurement is performed on 100 or more particles, and the average value is taken as the particle size of the fine particles.

  When the fine particles constituting the fine particle aggregate of the present invention are aggregates of a plurality of different types of fine particles, it is advantageous that the particle diameter of each fine particle is within the above range. Is preferable from the viewpoint that is reliably exhibited.

  The fine particles may have, for example, a spherical shape, a polyhedral shape, a spindle shape, a needle shape, or an indefinite shape. In particular, from the viewpoint of filling properties after sintering, a spherical shape is preferable.

  The fine particle aggregate of the present invention consisting of an aggregate of fine particles having the above-mentioned particle size is 1.0 μm or more and 10.0 μm or less on condition that the particle size is larger than the particle size of each fine particle. Is advantageous. In the case where the particle size of the fine particle aggregate is less than 1.0 μm, when the paste is prepared using the fine particle aggregate of the present invention, the viscosity of the paste is likely to increase, and the application of the paste is caused by that. It may be difficult to perform the operation. On the other hand, if the particle size exceeds 10.0 μm, it is difficult to increase the viscosity of the paste, but it may be difficult to form fine electrical wiring using the paste. From these viewpoints, the particle size of the fine particle aggregate is preferably 1.0 μm or more and 10.0 μm or less, and more preferably 2.0 μm or more and 7.0 μm or less. The particle size of the fine particle aggregate can be measured by, for example, the above-described image processing by SEM observation (MAC-View (Mountech Co., Ltd.)). The particle diameter of 100 or more fine particle aggregates is measured, and the average value is taken as the particle diameter of the fine particle aggregate.

  The fine particle aggregate may have a spherical shape, a polyhedral shape, a spindle shape, a needle shape, or an indefinite shape. In particular, a spherical shape is preferable from the viewpoint of the viscosity characteristics of the paste prepared from the fine particle aggregate and the filling property after sintering.

  The fine particle aggregate of the present invention has one of the characteristics in that the thermal shrinkage start temperature is low, although it has a relatively large particle size as described above. Specifically, it is advantageous that the fine particle aggregate has a thermal shrinkage start temperature of 80 ° C. or higher and 300 ° C. or lower. If the heat shrinkage starting temperature is less than 80 ° C., there may be inconveniences such as temperature control during storage and remelting after firing. On the other hand, when the thermal shrinkage start temperature exceeds 300 ° C., it may not be easy to form wiring for an electronic circuit on a flexible substrate made of a synthetic resin using a paste containing fine particle aggregates. From these viewpoints, the thermal shrinkage start temperature of the fine particle aggregate is preferably 100 ° C. or higher and 300 ° C. or lower, and more preferably 150 ° C. or higher and 250 ° C. or lower. The thermal shrinkage start temperature of the fine particle aggregate can be measured using, for example, a thermomechanical analyzer (TMA). TMA is measured by heating the powder pellets at 10 ° C./min in a 1 vol% hydrogen-99 vol% atmosphere. In this way, measurement is started from room temperature (25 ° C.), and a graph showing the relationship between temperature and displacement (%) is obtained. The relationship between the two is that the amount of displacement does not change in the low temperature region and becomes a flat graph, and the amount of displacement becomes negative (shrinks) as the temperature reaches the high temperature region. Or, depending on the case, due to variations in the production of pellets, after the displacement amount once rises to the plus (expansion) side in the low temperature range, the displacement amount finally decreases as the high temperature range is reached. Becomes minus (shrinkage). Therefore, in the present invention, when the graph of the amount of displacement changes from a flat state to minus as the temperature rises, the heat shrinkage start temperature is the temperature at which the amount of displacement is reduced by 0.1% from the flat state. Defined as starting temperature. In addition, when the displacement graph changes to increase once in the positive direction and then decrease in the negative direction as the temperature rises, the displacement amount decreases by 0.1% from the time when the displacement changes from rising to falling. This temperature is defined as the heat shrinkage start temperature. The pellets were manufactured by putting 500 mg of powder into an aluminum cup having a diameter of 4.0 mm and press-molding it at 1.0 MPa.

  In order for the fine particle aggregate of the present invention to exhibit the above-described heat shrinkage start temperature, it is important to set the particle size of the fine particles constituting the aggregate within the above-described range.

  As described above, the fine particle aggregate of the present invention is composed of a plurality of fine particles. This aggregated state is preferably maintained against the external force applied during the preparation of the paste using the fine particle aggregate of the present invention from the viewpoint of preventing an increase in the viscosity of the paste. For the same reason, it is preferable that the aggregated state is maintained against the external force applied while applying the prepared paste to the object. However, if the resistance to external force is excessively high, the thermal shrinkage start temperature tends to increase. In consideration of these matters, the fine particles of the present invention can be used when the force when the fine particle aggregate is crushed by pressing with a fine needle is used as a measure representing the degree to which the aggregate state of the fine particles can be maintained against external force. The scale of the aggregate is preferably from 0.01 N to 1 N, and more preferably from 0.1 N to 0.5 N.

  The above-mentioned scale can be measured with a micro compression tester (MCT-W201 manufactured by Shimadzu Corporation) using a φ50 μm indenter at a temperature of 25 ° C.

  In order to maintain the aggregated state of the fine particles described above, in the present invention, the aggregated state of a plurality of fine particles is maintained, for example, by van der Waals attractive force acting between the particles. Alternatively, the contact point between the fine particles is maintained by being slightly melted and fused. Alternatively, when a fine particle assembly is manufactured using a binder that bonds fine particles, the fine particles are maintained by the binding force of the binder.

  In particular, it is preferable that the fine particle aggregate of the present invention contains a binder, and the state of the aggregate is maintained by bonding the fine particles by the binding force expressed by the binder. As a result, the state of aggregation of the fine particles can be successfully maintained during the preparation of the paste and during the application of the paste, and the heat shrinkage start temperature is hardly increased. Moreover, since the surface of each fine particle is covered with the binder by using the binder, the fine particle is hardly oxidized. This also makes it difficult for the heat shrink start temperature to rise. Considering these matters, it is preferable to use an organic polymer material as a binder.

  Examples of the organic polymer material include polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene glycol, and polyvinyl acetate. These organic polymer materials can be used singly or in combination of two or more. In particular, it is preferable to use polyvinyl alcohol because it has many alcohol groups in the molecule and has high binder ability.

  When the organic polymer material is contained in the fine particle aggregate of the present invention, the proportion of the organic polymer material in the fine particle aggregate is preferably 0.01% by mass or more and 10% by mass or less. More preferably, the content is 1% by mass or more and 4.0% by mass or less. By setting the proportion of the organic polymer material within this range, it is possible to suppress an increase in the heat shrinkage start temperature of the fine particle aggregate while maintaining the fine particle aggregation state.

  The proportion of the organic polymer material in the fine particle aggregate can be measured, for example, by the following method. That is, the fine particle aggregate is analyzed using TG-MS, and the mass distribution measured therefrom can be obtained.

  The fine particle aggregate of the present invention preferably does not contain a surface treatment agent comprising an organic acid. In the technical field of metal fine particles, a surface treatment agent made of an organic acid is generally used for suppressing aggregation between fine particles. On the other hand, in the present invention, it is not necessary to suppress the aggregation of the fine particles, and the presence of the surface treatment agent may negatively affect the maintenance of the aggregate state of the fine particles. It is preferable to contain. Examples of the surface treatment agent comprising an organic acid include oleic acid, lauric acid, decanoic acid, nonanoic acid, octanoic acid, hexanoic acid, heptanoic acid and the like.

  Next, a preferred method for producing the fine particle aggregate of the present invention will be described. The fine particle aggregate is manufactured by collecting a plurality of fine particles constituting the fine particle aggregate by a predetermined means and maintaining the aggregated state. In order to assemble a plurality of fine particles, for example, a method using the binding force of a binder, a method of producing a granulated product by a spray drying method, a method of compressing a plurality of fine particles, and heating and fusing a plurality of particles. The method of making it wear etc. is mentioned. Among these methods, a method of producing a granulated product by a spray drying method is used because the aggregate state of the fine particles can be appropriately maintained and an increase in the heat shrinkage starting temperature of the fine particle aggregate can be suppressed. Is preferred.

  In the spray drying method, granulation is performed by supplying fine particles as raw materials and, if necessary, other components such as a binder made of an organic polymer material to the spray dryer. The flow rate of air flowing into the four-fluid nozzle when operating the spray dryer is preferably 10 L / min or more and 100 L / min or less. By setting the air flow rate to 10 L / min or more, it becomes easy to obtain a fine particle aggregate having a target particle size. From these viewpoints, the air flow rate to the nozzle is more preferably 30 L / min or more and 100 L / min or less, and further preferably 50 L / min or more and 100 L / min or less.

  The fine particles are preferably supplied to the spray dryer in a slurry state. In this case, the ratio of fine particles in the slurry is preferably 1.0% by mass or more and 50% by mass or less, and more preferably 5.0% by mass or more and 20% by mass or less. It is preferable to set the ratio of the fine particles within this range because a particle aggregate having a high fine particle density can be produced. The proportion of the binder used as necessary in the slurry is preferably 0.0001% by mass or more and 0.1% by mass or less, and more preferably 0.001% by mass or more and 0.04% by mass or less.

  The slurry to be supplied to the spray dryer may be aqueous based mainly on water or oil based mainly on an organic solvent. From the viewpoint of workability and safety when carrying out the spray drying method, it is preferable to use an aqueous slurry.

  The outlet temperature when operating the spray dryer is preferably 60 ° C. or higher and 130 ° C. or lower. By setting the inlet temperature to 60 ° C. or higher, the solid content can be sufficiently dried, and it becomes easy to obtain a granulated product with a small remaining liquid content. On the other hand, by setting the inlet temperature to 130 ° C. or lower, wasteful energy consumption and particulate oxidation can be suppressed.

  The granulated product produced by the spray drying method is generally spherical. The granulated product thus obtained is used as the fine particle aggregate of the present invention.

  When the fine particles contained in the slurry supplied to the spray dryer are fine particles made of copper, the copper fine particles are obtained by adding a reducing agent to an aqueous solution of a water-soluble copper compound, for example, and reducing copper ions in the aqueous solution to metallic copper. Can be manufactured. The total amount of the reducing agent may be added all at once, or may be added in two or more times. As the reducing agent, for example, hydrazine can be used. When copper fine particles are generated in the liquid by adding the reducing agent, aging is performed at a predetermined temperature for a predetermined time. According to this method, since a slurry of copper fine particles can be obtained directly, the slurry can be supplied to a spray dryer as it is or after adjusting the concentration of the copper fine particles.

  When cuprous oxide is used as the fine particles, for example, a method of mixing and stirring copper acetate, methanol and water, adding a reducing agent such as hydrazine to reduce the copper acetate, and generating cuprous oxide particles Can be used. Alternatively, a method of heating the acetylacetonato copper complex in a polyol solvent at about 200 ° C. can also be used.

  When metal-coated copper fine particles, for example, silver-coated copper fine particles are used as the fine particles, a displacement plating method or a reduction plating method is performed in a state where silver ions are present in the aqueous slurry of copper fine particles produced by the above-described method. The silver may be deposited on the surface of the copper particles.

  The fine particle aggregate made of the granulated product obtained by the above method is used in the form of a conductive composition containing the fine particle aggregate. For example, it is used in the form of conductive paste or conductive ink. This conductive paste contains the fine particle aggregate of the present invention, an organic vehicle, and glass frit. This organic vehicle includes a resin component and a solvent. Examples of the resin component include acrylic resin, epoxy resin, ethyl cellulose, carboxyethyl cellulose, and the like. Examples of the solvent include terpene solvents such as terpineol and dihydroterpineol, and ether solvents such as ethyl carbitol and butyl carbitol. Examples of the glass frit include borosilicate glass, borosilicate barium glass, and borosilicate zinc glass. The proportion of the fine particle aggregate in the conductive paste is preferably 36 to 97.5% by mass. The ratio of the glass frit is preferably 1.5 to 14% by mass. The proportion of the organic vehicle is preferably 1 to 50% by mass. As the conductive component in the conductive paste, only the fine particle aggregate of the present invention may be used, or the fine particle aggregate and other copper fine particles may be used in combination. By using the fine particle aggregate of the present invention in combination with other copper fine particles, it becomes easy to adjust the viscosity of the paste more precisely.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” means “mass%”.

[Example 1]
(1) Production of Copper Fine Particles The copper fine particle synthesis in this example corresponds to Example 1 of Patent Document 3 (Japanese Patent Laid-Open No. 2003-342621). However, the addition rate of the hydrated hydrazine described below was made faster than Example 1 of Patent Document 3. That is, 4 kg of copper sulfate (pentahydrate) and 120 g of aminoacetic acid were dissolved in water to prepare an 8 L aqueous copper salt solution having a liquid temperature of 60 ° C. While stirring this aqueous solution, 5.75 kg of 25% sodium hydroxide solution was quantitatively added over about 5 minutes, and stirring was performed at a liquid temperature of 60 ° C. for 60 minutes. Cupric oxide was produced by aging until the color of the liquid was completely black. After standing for 30 minutes, 1.5 kg of glucose was added and the mixture was aged for 1 hour to reduce cupric oxide to cuprous oxide. Thereafter, the liquid temperature was raised to 70 ° C., and 1 kg of hydrated hydrazine was quantitatively added over 2 minutes to reduce cuprous oxide to obtain copper particles. The aqueous copper fine particle slurry thus obtained was washed with a rotary filter until the conductivity reached 50 μS. When the particle size of the copper fine particles in the obtained aqueous slurry was measured by image processing using SEM, the D ₅₀ value was 150.0 nm. A scanning electron microscope image of the fine particles is shown in FIG. As is clear from the figure, the copper fine particles were spherical.

(2) Granulation of Fine Particle Aggregate Polyvinyl alcohol as a polymer organic compound was added to the aqueous slurry of copper fine particles obtained in the preceding item (1) to obtain a slurry for supply to a spray dryer. The concentration of copper fine particles in this supply slurry was 17.0%, and the concentration of polyvinyl alcohol was 1.0% with respect to the particles. The obtained slurry for supply was supplied to a spray dryer (manufactured by Fujisaki Electric Co., Ltd.) and granulated and dried to obtain a fine particle aggregate made of the granulated product. The operating conditions of the spray dryer were as follows.
・ Slurry supply speed: 100 mL / min
・ Nozzle air flow rate: 90mL / min
・ Outlet temperature: 70 ℃
When the particle size of the obtained fine particle aggregate was measured by image processing by SEM observation, the D ₅₀ value was 3.2 μm. The proportion of polyvinyl alcohol in the fine particle aggregate was 1.0%. A scanning electron microscope image of this fine particle assembly is shown in FIG. As is clear from the figure, this fine particle aggregate was spherical.

[Example 2]
In Example 1, polyvinyl alcohol was not added to the slurry for supply to the spray dryer. Except this, it carried out similarly to Example 1, and obtained the fine particle aggregate | assembly consisting of a granulated material. When the particle diameter of the obtained fine particle aggregate was measured by image processing by SEM observation, the D ₅₀ value was 3.7 μm. A scanning electron microscope image of this fine particle assembly is shown in FIG. As is clear from the figure, this fine particle aggregate was spherical.

Example 3
(1) Production of copper fine particles The copper fine particle synthesis in this example corresponds to Example 1 of Patent Document 4 (Japanese Patent Laid-Open No. 2009-74152). First, 6000 g of copper sulfate was added to 6.5 L of pure water and stirred, and then water was further added so that the liquid volume of the copper sulfate aqueous solution (copper salt aqueous solution) was 9 L while maintaining the liquid temperature at 50 ° C. Was added to adjust the concentration. To this copper sulfate aqueous solution, 2537 ml of an aqueous ammonia solution (concentration 25 wt%) was added in 30 minutes for neutralization to obtain a copper salt compound slurry. The copper salt compound slurry was allowed to stand for 30 minutes for aging. Up to this point, the liquid temperature of the copper salt compound slurry was maintained at 50 ° C., but after aging, the liquid temperature was adjusted to 45 ° C. Next, the amount of liquid was adjusted by adding water so that the copper concentration of the copper salt compound slurry was 2.0 mol / L. This copper salt compound slurry was maintained at a pH of 6.3 and a liquid temperature of 50 ° C., and 450 g of hydrazine monohydrate (hydrazine reducing agent) and 591 ml of an aqueous ammonia solution (concentration 25%) as a pH adjuster were added. It added continuously over 30 minutes and was set as the cuprous oxide slurry. Then, in order to complete the reduction reaction, stirring was continued for another 30 minutes. Then, for repulp washing, after adding pure water to the cuprous oxide slurry and adjusting the liquid volume to 18 L, the operation is performed by allowing to stand and precipitating cuprous oxide particles, and removing 14 L of the supernatant after standing, Repeated until pH was 4.7. Then, 8 L of warm pure water was added to make the total liquid volume 12 L, the liquid temperature was maintained at 45 ° C., the copper concentration was adjusted to 2.0 mol / L, and this was used as a washed cuprous oxide slurry. To the washed cuprous oxide slurry after adjusting the copper concentration, 3.02 g of ammonium hypophosphite was added and stirred for 5 minutes (phosphorus compound addition step). Again, the amount of liquid was adjusted by adding water so that the copper concentration of the washed cuprous oxide slurry was 2.0 mol / L. To this washed cuprous oxide slurry, 1200 g of hydrazine monohydrate was added over 30 minutes. Next, the mixture was further stirred for 15 minutes to complete the reduction reaction and to reduce and precipitate the copper powder. The aqueous copper fine particle slurry thus obtained was washed with a rotary filter until the conductivity reached 50 μS. When the particle size of the copper fine particles in the obtained aqueous slurry was measured by image processing using SEM, the D ₅₀ value was 500 nm.

(2) Granulation of fine particle aggregate In Example 1, the amount of polyvinyl alcohol in the slurry for supply to the spray dryer was 2%. Except this, it carried out similarly to Example 1, and obtained the fine particle aggregate | assembly consisting of a granulated material. The resulting fine particle aggregates is spherical, was measured the particle size by image analysis by SEM observation, D ₅₀ value was 4.5 [mu] m.

[Comparative Example 1]
In Example 1, polyvinyl alcohol was not added to the slurry for supply to the spray dryer, but oleic acid was added instead. Except this, granulation was performed in the same manner as in Example 1. A scanning electron microscope image of the copper fine particles after granulation is shown in FIG. As shown in the figure, a granulated product could not be obtained. The proportion of oleic acid was 1% with respect to the copper fine particles.

[Comparative Example 2]
This comparative example is an example in which the copper particles themselves were produced. In Example 1, 1 kg of hydrated hydrazine was quantitatively added over 120 minutes to reduce cuprous oxide in the same manner as in Example 1. This is an example of obtaining copper particles. When the particle diameter of the obtained copper particles was measured by image processing by SEM observation, the D ₅₀ value was 3.9 μm.

[Evaluation 1]
TMA measurement was performed about the Example and the comparative example. EXSTAR6000 (manufactured by Seiko Instruments Inc.) was used as a measuring device. The atmosphere was 1% hydrogen-99% nitrogen, and the measurement was performed at a heating rate of 10 ° C./min. The result is shown in FIG. In addition, Table 1 below shows the thermal shrinkage start temperatures determined from the graph of FIG.

[Evaluation 2]
About the Example and the comparative example, the electrically conductive paste was prepared and the viscosity in 25 degreeC was measured. The results are shown in Table 1. In the conductive paste, the proportion of copper was 80%, the proportion of terpineol as a solvent was 13%, and the proportion of resin was 7%. For the viscosity measurement, Rheo Stress 3000 (manufactured by Thermo Scientific Co., Ltd.) was used.

[Evaluation 3]
About the Example and the comparative example, the crushing force of the fine particle aggregate was measured. The results are shown in Table 1.

  As is apparent from the results shown in FIG. 5 and Table 1, according to each example, it can be seen that the thermal shrinkage start temperature of copper is low and the viscosity of the paste is low. On the other hand, in the comparative example, although the heat shrinkage start temperature of copper is low, it can be seen that the viscosity of the paste increases.

Claims (9)

A copper-containing fine particle aggregate formed by aggregating a plurality of fine particles containing copper and having a particle size of 10 nm to 600 nm,
A copper-containing fine particle aggregate having a heat shrinkage starting temperature of 80 ° C. or higher and 300 ° C. or lower and a particle size of 1.0 μm or higher and 10.0 μm or lower in a 1 vol% hydrogen-99 vol% nitrogen atmosphere.   The copper-containing fine particle aggregate according to claim 1, further comprising an organic polymer material.   The copper-containing fine particle aggregate according to claim 1 or 2, which does not contain a surface treatment agent comprising an organic acid.   The copper-containing fine particle assembly according to any one of claims 1 to 3, wherein the fine particles are made of copper, cuprous oxide, or core particles made of copper are coated with silver. body.   The copper-containing fine particle aggregate according to any one of claims 1 to 4, comprising a granulated body granulated by a spray drying method.   A method for producing a copper-containing fine particle aggregate comprising a step of collecting a plurality of fine particles containing copper and having a particle diameter of 10 nm to 600 nm by spray drying.   The production method according to claim 6, wherein the fine particles are subjected to a spray drying method together with an organic polymer material.   The production method according to claim 6 or 7, wherein the fine particles are subjected to a spray drying method in the absence of a surface treatment agent composed of an organic acid.   A conductive composition comprising the copper-containing fine particle aggregate according to any one of claims 1 to 5.