JP2017025371A - Silver-coated copper powder and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silver-coated copper powder having excellent compatibility and dispersibility with a solvent, a resin and the like in a paste using a silver-coated copper powder without being affected by a residue of a silver plating solution component, and a method for producing the same. offer. SOLUTION: The silver-coated copper powder 1 in which the surface of copper particles is coated with silver, the core material 2 using the copper particles, the silver layer 3 in which the surface of the core material 2 is coated with silver, and the silver layer 3 It has an organic coating layer 4 formed by adsorbing a cationic surfactant and a dispersant, and the organic coating layer 4 has an internal friction angle of 20 ° or less and is made of a 50% by volume aqueous solution of methanol. The contact angle is 100 ° or more. [Selection diagram] Fig. 1

Description

  The present invention relates to a silver-coated copper powder and a method for producing the same, and more specifically, a silver-coated copper powder that is a main component of a silver-coated copper powder paste used for forming a wiring layer or an electrode of an electronic device, and It relates to the manufacturing method.

  Silver pastes such as resin-type silver paste and fired-type silver paste are used for the formation of wiring layers and electrodes in electronic devices. However, in recent years, copper powder, which is cheaper than silver, has been used to reduce costs. Has been tried. However, in the case of copper powder, since the surface is easily oxidized, an oxidation resistance treatment is required. As an oxidation resistance treatment, a method of coating a copper surface with a metal such as nickel or tin has been attempted. However, a metal such as nickel or tin is inferior to copper or silver in terms of conductivity, so oxidation resistance and conductive properties However, the use of silver-coated copper powder in which good copper is coated on the copper surface is progressing.

  The silver-coated copper powder is applied as a paste, applied or printed, and then heat-cured or heat-fired to form a conductive film that becomes a wiring layer, an electrode, or the like. For example, the resin-type paste is made of silver-coated copper powder, resin, curing agent, solvent, etc., printed on the conductor circuit pattern or terminal of the substrate, and heat-cured at 100 ° C. to 200 ° C. to form a conductive film, Wiring and electrodes are formed. In wirings and electrodes formed of these silver-coated copper pastes, electrically connected current paths are formed by continuous silver-coated copper powder.

  The silver-coated copper powder used in the silver-coated copper paste has a different particle size depending on the thickness of the wiring to be formed and the thickness of the electrode. Further, by uniformly dispersing the silver-coated copper powder in the paste, it is possible to form a wiring having a uniform thickness and an electrode having a uniform thickness.

  It is also important that the silver-coated copper powder has a uniform particle size, little aggregation, and high dispersibility in the paste. This is because if the particle size is uniform and the dispersibility in the paste is high, curing or firing proceeds uniformly, and a conductive film having low resistance and high strength can be formed. Silver-coated copper powder has non-uniform particle size and poor dispersibility, and since silver-coated copper particles are not uniformly present in the printed film, the thickness and thickness of the wiring and electrodes are not uniform, and the coating is cured. 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.

  Since silver-coated copper powder is used as a substitute for silver powder, it is used in the same manner as silver paste. Moreover, since the outermost surface of silver coat copper powder is silver, when using it by making it into a paste, it is thought that the method similar to the manufacturing method of silver powder is suitable. Silver powder, which occupies most of the weight in the silver paste, not only has a uniform particle size and little aggregation, but also has a good affinity for vehicles made of solvents, resins, etc., and has high dispersibility in the silver paste. Characteristics are required. Such characteristics vary depending not only on the structural properties of the powder such as bulk density and particle size distribution but also on the chemical properties of the silver powder surface such as the slipperiness of the powder surface, hydrophilicity and hydrophobicity.

  Regarding silver powder used for silver paste, for example, Patent Document 1 describes that spherical silver powder has a specific bulk density and compact density, thereby improving compatibility with a vehicle or a resin. Yes. However, in Patent Document 1, there is a description that it is preferable to add a dispersant to the slurry-like reaction system before or after the reduction precipitation of the silver powder, but there is no description about the detailed chemical properties of the silver powder surface. It is difficult to control the compatibility with the vehicle and the resin simply by mixing such structural parameters and the dispersing agent into the slurry. Patent Document 1 does not describe a method for producing silver powder, such as a method for crushing silver powder, which greatly affects the chemical properties of the silver powder surface.

Further, Patent Document 2, aggregation and _{D 50} values by the particle size distribution measurement, SEM the ratio _D 50 _{/ D IA} with particle size _{D IA} values obtained by the image analysis (scanning electron microscope) observation image of the powder As a measure of the degree, it is described as low cohesiveness if it is below a specific value. Thus, if the D ₅₀ / D _IA value is small, the number of aggregates in the powder is considered to be small. However, in Patent Document 2, as in Patent Document 1, a description relating to the chemical properties of the silver powder surface affecting the compatibility between the vehicle and the resin when making a paste and a description relating to the production method affecting the chemical properties. There is no.

  Therefore, as for the silver-coated copper powder, as in Patent Document 1 and Patent Document 2, the solvent of the silver-coated copper powder paste, which is sufficient only by structural properties such as bulk density, compact density, and powder cohesion, The compatibility and dispersibility with resin and the like cannot be improved. For this reason, the silver coat copper powder is calculated | required for the further improvement of compatibility and a dispersibility.

  On the other hand, as a method for improving the dispersibility in the paste, Patent Document 3 discloses that in the method for producing silver powder, two or more kinds of dispersants, preferably benzotriazole, stearic acid, A method for producing silver powder is disclosed in which two or more kinds of dispersants including a hydrophobic dispersant such as oleic acid and a hydrophilic dispersant such as gelatin or collagen peptide are added. Also in silver coat copper powder, it is thought that adding two or more kinds of dispersing agents mentioned above is effective in improving the dispersibility in the paste.

  Moreover, in patent document 4, in order to make it easy to crush aggregation of silver coat copper powder, the silver coat copper powder which coat | covered the surface with the fatty acid is disclosed.

  However, in the production of silver-coated copper powder, the surface of the copper powder is widely plated with a silver plating solution in the step of coating the surface of the copper powder with silver. Some of these silver plating solutions are intended to uniformly coat silver, and particularly to prevent re-deposition of dissolved copper in substitutional silver plating solutions. For example, as disclosed in Patent Document 5, a complexing agent (chelating agent) such as ethylenediamine tetraacetate is also widely used. After finishing the silver coating on the copper powder, the plating solution components such as these complexing agents are washed and removed. However, a part of the plating solution component may remain on the surface of the silver-coated copper powder, and even if a dispersant is added, sufficient dispersibility in the paste may not be obtained. In order to suppress this, as a result of taking measures such as strengthening the washing after the silver coating step, the productivity was lowered and the production cost was increased.

JP 2006-097086 A JP 2004-100013 A JP 2008-088453 A JP 2005-044798 A JP-A-10-212501

  Therefore, in view of the above-described conventional circumstances, the present invention is compatible with a solvent, a resin, and the like in a paste using silver-coated copper powder without being affected by the residue of the silver plating solution component. It aims at providing the outstanding silver coat copper powder and its manufacturing method.

  That is, the silver-coated copper powder according to one embodiment of the present invention for achieving the above object is a silver-coated copper powder in which the surface of the copper particles is coated with silver, and the core material using the copper particles and the core material A silver layer covering silver on the surface, and an organic coating layer formed by adsorbing a cationic surfactant and a dispersant on the silver layer, and the internal coating layer has an internal friction angle of 20 °. And the contact angle with a 50% by volume aqueous solution of methanol is 100 ° or more.

  In one embodiment of the present invention, the surface SP value by the acetone titration method is preferably 18 or less.

  In one embodiment of the present invention, it is preferable that the core material has any one of a spherical shape, a flake shape, a dendritic shape, a disc shape, and an ellipsoid shape, and has an average particle diameter of 0.1 μm to 20 μm.

  In one aspect of the present invention, the amount of silver coated on 100% by mass of the entire silver-coated silver-coated copper powder is preferably 0.5% by mass to 50% by mass.

  In one embodiment of the present invention, the cationic surfactant is preferably a quaternary ammonium salt type.

  In one embodiment of the present invention, the dispersant is preferably a fatty acid or a salt thereof.

  Moreover, in the manufacturing method of the silver coat copper powder which concerns on the other aspect of this invention, it is a manufacturing method of the silver coat copper powder which used the copper particle as a core material, and was equipped with the silver layer on the surface of the core material, Comprising: After the silver coat copper particle slurry obtained in the silver coat treatment step and the silver coat treatment step to form the silver layer is solid-liquid separated, the surface treatment is performed with a cationic surfactant and a dispersant to form the surface of the silver coat copper particles. The surface treatment step for forming the organic coating layer, and the silver-coated copper particles for forming the organic coating layer obtained in the surface treatment step, using a high-speed stirrer, the peripheral speed of the stirring blade is 10 m / second or more and 40 m / second or less. And a crushing step for crushing, and in the surface treatment step, the silver-coated copper is such that the internal friction angle is 20 ° or less and the contact angle in a 50% by volume aqueous methanol solution is 100 ° or more. Forming an organic coating layer on the surface of the particles. Features.

  In one embodiment of the present invention, it is preferable to form an organic coating layer on the surface of the silver-coated copper particles by adding 0.01% by mass to 3.00% by mass of the dispersant.

  In one aspect of the present invention, the crushing step preferably crushes the silver-coated copper particles at a crushing time of 10 minutes to 60 minutes.

  In one aspect of the present invention, it is preferable to have a washing step for washing copper particles as a pre-step of the silver coating treatment step.

  In the present invention, the internal friction angle of the silver-coated copper powder is 20 ° or less, and the contact angle in the methanol 50% by volume aqueous solution is 100 ° or more, so that it is affected by the residue of the silver plating solution component. In particular, it is highly compatible with hydrophobic solvents, resins, etc., has excellent dispersibility, and can be easily pasted. Thereby, in this invention, the quality and productivity of the paste using silver coat copper powder can be improved. Further, even after being stored at room temperature after production, the internal friction angle of the silver-coated copper powder hardly changes and maintains 20 ° or less. Therefore, aggregation of the silver coated copper powder due to changes over time is suppressed, and quality control of the paste using the silver coated copper powder becomes easy.

  In the present invention, it is also possible to produce a silver-coated copper powder that is highly compatible with hydrophobic solvents, resins, etc., has excellent dispersibility, and can be easily pasted.

It is a figure which shows typically about the surface state of the silver coat copper powder which concerns on embodiment of this invention. It is process drawing of the manufacturing method of the silver coat copper powder which concerns on embodiment of this invention.

Below, the silver coat copper powder to which this invention is applied, and its manufacturing method are demonstrated. Note that the present invention is not limited to the following detailed description unless otherwise specified. Embodiments of a silver-coated copper powder to which the present invention is applied and a method for producing the same will be described in detail in the following order.
1. Silver-coated copper powder 1-1. Heartwood 1-2. Silver layer 1-3. 1. Organic coating layer 2. Manufacturing method of silver coat copper powder 2-1. Cleaning step 2-2. Silver coat treatment process 2-3. Surface treatment process 2-4. 2. Crushing process Summary

[1. Silver coated copper powder]
The silver coat copper powder 1 which concerns on this Embodiment is provided with the core material 2, the silver layer 3, and the organic coating layer 4, as shown in FIG. Here, what formed the silver layer 3 in the core material 2 is called the silver coat copper particle 5. FIG.

  The present inventor has found the invention of silver-coated copper powder as follows. For example, copper powder as a paste agent has poor oxidation resistance and significant deterioration in quality. On the other hand, with silver powder as a paste agent, the raw material cost is too high. However, silver generally has high conductivity and the like. Therefore, the silver coat copper particle 5 formed by coat | covering silver on copper can take over the performance. Compared to the case where gold, silver, or palladium is used as the core material 2, there is an advantage that the cost can be reduced when copper powder is used.

  Moreover, when forming a silver layer using aluminum as a core material, an oxide film is formed on the surface of aluminum, and a silver layer cannot be formed on the surface of aluminum. On the other hand, when forming a silver layer using copper as a core material, a silver layer can be formed without forming an oxide film on the surface of copper.

<1-1. Heartwood>
In the silver coat copper powder 1 according to the present embodiment, copper particles are used as the core material 2.

  Although the shape of the copper particles as the core material 2 is not particularly limited, a spherical shape, a flake shape, a dendritic shape, a disc shape, an ellipsoidal shape, or the like can be used. Two or more different shapes can be used in combination.

<1-2. Silver layer>
In the silver-coated copper powder 1 according to the present embodiment, the silver layer 3 covers the surface of the core material 2 with silver. By covering silver, this is excellent in electrical connection when the silver-coated copper powder 1 is pasted.

  In the silver coat copper powder 1 which concerns on this Embodiment, it is preferable that 0.5 mass%-50 mass% are coat | covered with respect to 100 mass% of the whole silver coat copper powder which silver coat | covered the silver amount. . The silver coating amount is preferably as small as possible from the viewpoint of cost. On the other hand, if the coating amount is too small, a uniform silver coating cannot be secured on the copper surface, which causes a decrease in conductivity. Therefore, the coating amount is preferably 0.5% by mass or more, more preferably 5% by mass or more, and further preferably 10% by mass or more with respect to 100% by mass of the entire silver-coated silver-coated copper powder.

  On the other hand, if the silver coating amount increases, it is not preferable from the viewpoint of cost, and if silver is coated on the copper surface more than necessary, the fine protrusions derived from the copper particles are lost, so the silver coating amount is silver coated silver. 50 mass% or less is preferable with respect to 100 mass% of the whole coated copper powder, 40 mass% or less is more preferable, and 20 mass% or less is more preferable.

<1-3. Organic coating layer>
In the silver coat copper powder 1 according to the present embodiment, the organic coating layer 4 is formed by adsorbing a cationic surfactant and a dispersing agent to the silver layer 3.

  The silver coat copper powder 1 which concerns on this Embodiment is a paste using the silver coat copper powder 1 by providing the organic coating layer 4 formed by adsorb | sucking a cationic surfactant, solvent and resin Etc. and the dispersibility is excellent. Therefore, such a silver coat copper powder 1 becomes easy to paste.

  For example, when using a copper particle as the core material 2 and obtaining a silver coat copper particle slurry in the silver coat process which forms the silver layer 3 on the surface of the copper particle, a cationic surfactant is used as the surfactant. Since the cationic surfactant is ionized into positive ions, an effect of improving the adsorptivity to the silver-coated copper particles 5 can be obtained.

  The cationic surfactant is not particularly limited, but is an alkyl monoamine salt type represented by a monoalkylamine salt, an alkyl diamine salt represented by an N-alkyl (C14 to C18) propylenediamine dioleate. Type, quaternary ammonium salt type such as alkyldipolyoxyethylenemethylammonium chloride and alkyltrimethylammonium salt type represented by alkyltrimethylammonium chloride and alkyldimethylbenzylammonium salt type represented by alkyldimethylbenzylammonium chloride, alkylpyridinium Salt type, tertiary amine type typified by dimethylstearylamine, polyoxyethylene alkylamine type typified by polyoxypropylene / polyoxyethylene alkylamine, N, N ′, '- tris (2-hydroxyethyl) -N- alkyl (C14 -C18) at least one selected from an oxyethylene addition type diamines typified by 1,3-diaminopropane are preferred. These cationic surfactants have high adsorptivity to the silver-coated copper particles 5, and plating solution components such as complexing agents generally contained in the silver plating solution described later remain on the surface of the silver-coated copper particles 5. Even if it did, the uniform organic coating layer 4 can be formed. This effect is high in the quaternary ammonium salt type and the tertiary amine salt type among the cationic surfactants, and it is more preferable to use any one or a mixture thereof. Here, C14 to C18 means having 14 to 18 carbon atoms.

  The cationic surfactant preferably has at least one alkyl group having 4 to 36 carbon atoms represented by methyl group, butyl group, cetyl group, stearyl group, beef tallow, hard beef tallow, and plant stearyl. Moreover, as an alkyl group, it is preferable that at least 1 sort (s) selected from polyoxyethylene, polyoxypropylene, polyoxyethylene polyoxypropylene, polyacrylic acid, and polycarboxylic acid is added.

  The cationic surfactant is not particularly limited, and is at least one selected from a fluoride salt, a bromide salt, an iodide salt, a chloride salt, a sulfate salt, a nitrate salt, a phosphate salt, and an acetate salt. Preferably there is. These are preferable because they are generally contained as a main component of the surfactant and are easily available.

  The addition amount of the cationic surfactant is preferably in the range of 0.002 mass% to 1.000 mass% with respect to the silver-coated copper particles 5. Since almost the entire amount of the cationic surfactant is adsorbed on the silver-coated copper particles 5, the addition amount of the surfactant and the adsorption amount are substantially equal. When the addition amount of the cationic surfactant is less than 0.002% by mass, the effect of suppressing aggregation of the silver-coated copper particles 5 and improving the adsorptivity of the dispersant may not be obtained. On the other hand, when the addition amount of the cationic surfactant exceeds 1.000 mass%, the conductivity of the wiring layer or electrode formed using the paste of the silver-coated copper powder is not preferable.

  Next, as the dispersant, for example, protective colloids such as fatty acids, organometallics, and gelatin can be used. However, in view of adsorbability with cationic surfactants without fear of contamination with impurities, fatty acids or their It is preferable to use a salt. In addition, you may add a fatty acid or its salt as an emulsion.

  The fatty acid or salt thereof used as the dispersant is not particularly limited, but at least one selected from stearic acid, oleic acid, myristic acid, palmitic acid, linoleic acid, lauric acid, and linolenic acid, or these It is preferably at least one salt selected from the listed fatty acids. This is because these fatty acids or salts thereof have a relatively low boiling point, so that there is little adverse effect on wiring layers and electrodes formed using the silver-coated copper paste. Fatty acids or salts thereof are inherently hydrophobic, and abundantly exist on the outer surface side of the organic coating layer 4 by adsorbing a dispersing agent on the surface of the silver-coated copper particles 5 via a cationic surfactant. It is considered that the silver-coated copper powder 1 has hydrophobicity. In particular, by selecting a surfactant that easily adsorbs to the silver-coated copper particles 5, for example, a charge that is ionized to a charge opposite to the surface of the silver-coated copper particles 5, the surfactant can be sufficiently passed through a cationic surfactant. A dispersing agent can be made to adsorb | suck and the silver coat copper powder 1 comes to show sufficient hydrophobicity.

  Further, when the fatty acid or a salt thereof is adsorbed as a dispersant via a cationic surfactant on the surface of the silver-coated copper particles 5, the internal friction angle described above changes over time as compared with the case where the dispersant is not adsorbed. It becomes difficult to do. This is presumably because a large amount of fatty acid or salt thereof is present on the outer surface side of the organic coating layer 5 and the effect of protecting the organic coating layer 4 is obtained. Due to this effect, when the silver-coated copper powder 1 is manufactured and stored in a properly controlled state and then mixed with a solvent to form a paste, the internal friction angle of the silver-coated copper powder 1 is maintained at 20 ° or less. Yes. Here, storing in a properly managed state means storing the silver-coated copper powder 1 in a container, bag or the like as an example, and then storing it at room temperature (20 ° C. to 30 ° C.).

  The addition amount of the dispersant is preferably in the range of 0.01% by mass to 3.00% by mass with respect to the silver-coated copper particles 5, and more preferably 0.01% by mass to 1.00% by mass. The amount adsorbed on the silver-coated copper particles 5 varies depending on the type of the dispersant, but when the added amount is less than 0.01% by mass, an amount of dispersion that can sufficiently obtain the effect of suppressing aggregation of the silver-coated copper particles 5 is obtained. The agent may not be adsorbed on the silver-coated copper particles 5. On the other hand, when the added amount of the dispersant exceeds 3.00% by mass, the dispersant adsorbed on the silver-coated copper particles 5 increases, and the wiring layer or electrode formed using the silver-coated copper powder paste is increased. In some cases, sufficient conductivity cannot be obtained.

  A silver-coated copper powder 1 shown in FIG. 1 is contained in a resin-type silver-coated copper powder paste composed of a curing agent, a resin, a solvent, and the like. The resin-type silver-coated copper powder paste containing the silver-coated copper powder 1 is used for forming wiring layers and electrodes. Therefore, the silver-coated copper powder 1 has good compatibility with the solvent and resin of the silver-coated copper powder paste so that electrical connection can be achieved, and it is necessary to disperse the paste in the paste without deviation. The silver-coated copper powder 1 is particularly suitable for a silver-coated copper powder paste using a hydrophobic solvent.

(Internal friction angle)
First, the internal friction angle of the silver coat copper powder 1 will be described. Here, the internal friction angle of the silver-coated copper powder 1 refers to the internal friction angle of the organic coating layer 4 corresponding to the surface of the silver-coated copper powder 1.

  Silver-coated copper powder 1 according to the present embodiment has an internal friction angle of 20 ° or less. The internal friction angle is a parameter representing the slipperiness of the powder, and the internal friction angle can be measured by a commercially available powder layer shear force measuring device. In the case of the silver coated copper powder 1 for paste, when the internal friction angle exceeds 20 °, the slip between the particles becomes worse. As a result, when forming a paste, the solvent or resin cannot be divided between the particles of the silver-coated copper powder 1, and only a part of the surface of the silver-coated copper powder 1 can be wetted. In such a state, even if agitation is performed, the particles are hardly loosened and the dispersibility of the silver-coated copper powder 1 is poor.

  Here, the silver-coated copper powder 1 having poor dispersibility not only takes time for pre-kneading to wet and disperse the components, but the silver-coated copper powder 1 aggregated during the main kneading by a three-roll mill or the like is pressed. It is crushed and silver flakes are easily generated.

  Accordingly, the silver-coated copper powder 1 according to the present embodiment has a good slip due to the internal friction angle being 20 ° or less, and the solvent and the resin enter between the particles, so that the compatibility is improved. Dispersibility in the copper powder paste is improved.

(Contact angle)
Next, the contact angle of the silver-coated copper powder 1 will be described. Here, the contact angle of the silver-coated copper powder 1 refers to the contact angle of the organic coating layer 4 corresponding to the surface of the silver-coated copper powder 1.

  Silver-coated copper powder 1 according to the present embodiment has a contact angle of 100 ° or more. The contact angle is a parameter representing the wettability of the surface of the silver-coated copper powder 1 with respect to the solvent. For example, the greater the contact angle with water, the easier the wet with the hydrophobic paste solvent. On the other hand, the smaller the contact angle with water, the more hydrophilic and the wetness with respect to the hydrophobic paste solvent becomes worse. The contact angle of the silver-coated copper powder 1 is generally measured on the molded surface. However, when measuring with water, it is difficult to measure with high accuracy because a powder with high hydrophobicity has a spherical shape on the surface of the molded powder and the water droplet slides and moves.

  For this reason, a method of performing measurement by adding a low polarity solvent such as methanol to water and lowering the polarity of the solvent is performed. In producing a silver-coated copper powder paste, generally a hydrophobic solvent is often used.

  Accordingly, when the silver-coated copper powder 1 according to the present embodiment has a hydrophilic surface with a contact angle of less than 100 °, the compatibility of the paste with the solvent or resin is poor, and the silver-coated copper powder 1 and the solvent or resin It becomes difficult to make a paste. In addition, when the mixture is forcibly kneaded into a paste, the dispersion stability is poor and the paste is likely to be separated by reaggregation.

(Surface SP value)
Next, the surface SP value of the silver-coated copper powder 1 will be described. Here, the surface SP value of the silver-coated copper powder 1 refers to the SP value of the organic coating layer 4 corresponding to the surface of the silver-coated copper powder 1.

  Silver-coated copper powder 1 according to the present embodiment has a surface SP value of 18 or less. The surface SP value is a parameter representing the polarity of the surface of the silver-coated copper powder 1, and the smaller the value, the more hydrophobic the surface SP value.

  The surface SP value can be measured by a commercially available powder wettability tester or the like, but simply, an acetone titration method as described in “Coloring Materials, 62 (9) 524-528”. But measurement is possible. In this acetone titration method, a hydrophobic powder is added to water (A [mL]) and suspended. While gently stirring with a stirrer, acetone is dropped with a burette, and the dripping amount of acetone (B [mL]) required until the powder wets and settles is measured. The SP value of water 23.43, the SP value of acetone 9.75, the volume of water used and the SP value of the acetone solution precipitated from the volume of acetone used were calculated from the following formula 1, and these values were calculated using silver-coated copper powder. The surface SP value is 1.

  When the surface SP value of the silver-coated copper powder 1 is larger than 18, the hydrophilicity is too large, and the compatibility of the paste with the solvent or resin is deteriorated, and the wetness between the silver-coated copper powder 1 and the solvent or resin occurs. Therefore, it becomes difficult to form a paste. Moreover, even if it is kneaded forcibly to make a paste, the dispersion stability is poor, and the paste is easily separated by reaggregation.

  On the other hand, when the surface SP value of the silver-coated copper powder 1 is 18 or less, the hydrophilicity of the silver-coated copper powder 1 does not become too large, the compatibility with the solvent and the resin is good, and the dispersibility is excellent. It becomes. For this reason, when the surface SP value of the silver coat copper powder 1 is 18 or less, the silver coat copper powder 1 can be easily pasted. Therefore, the silver coat copper powder 1 which concerns on this Embodiment shall have surface SP value of 18 or less.

  The silver coat copper powder 1 surface-treats the silver coat copper particle 5 obtained by coat | covering the silver on the surface using a copper particle for the core material 2, and the organic coating layer 4 on the particle | grain surface like FIG. Is formed, the above-mentioned internal friction angle can be made 20 ° or less, the contact angle can be made 100 ° or more, and the surface SP value by the acetone titration method can also be made 18 or less. This organic coating layer 4 can be formed of a cationic surfactant.

  In the silver-coated copper powder 1, by using a cationic surfactant, the adsorptivity of the cationic surfactant to the silver-coated copper particles 5 is greatly improved, so that the surfactant is firmly attached to the silver-coated copper particles 5. Even if a plating solution component such as a complexing agent contained in the silver plating solution remains on the surface of the silver-coated copper particles 5, a uniform organic film can be formed. More preferably, by stably adsorbing the cationic surfactant adsorbed on the silver-coated copper particles 5, the silver-coated copper powder 1 which is further suppressed in aggregation and excellent in dispersibility in the paste is obtained. Can do.

[2. Method for producing silver-coated copper powder]
Hereinafter, the manufacturing method of the silver coat copper powder which concerns on this Embodiment is demonstrated for every process in detail. As shown in the process diagram of FIG. 2, the silver-coated copper powder manufacturing method according to the present embodiment includes a silver coating treatment step S <b> 1 that covers the surface of copper particles as the core material 2 and silver-coated copper particles 5. A surface treatment step S2 for forming the organic coating layer 4 on the surface thereof, and a crushing step S3 for crushing the silver-coated copper particles 5 forming the organic coating layer 4 obtained in the surface treatment step S2. Furthermore, in the manufacturing method of the silver coat copper powder which concerns on this Embodiment, it is preferable to provide a washing | cleaning process (not shown) before silver coat processing process S1.

<2-1. Cleaning process>
In the washing step, the copper particles are dispersed in the washing liquid and washed with stirring. Specifically, this washing is preferably performed with an acidic solution, and more preferably, a polyvalent carboxylic acid that is also used in the reducing agent used in the silver coating treatment step S1. After washing the copper particles, the copper particles are filtered and separated and washed with water as appropriate to obtain a water slurry in which the copper particles are dispersed in water. In addition, what is necessary is just to use a well-known method for filtration, isolation | separation, and water washing.

  In the manufacturing method of the silver coat copper powder which concerns on this Embodiment, a silver layer can be coated on copper particle with uniform thickness by providing a washing process. For this reason, since the projection of the copper particle is entirely silver-coated with respect to the paste prepared from the silver-coated copper powder to be produced in the future, the problem of deterioration in electrical characteristics does not occur.

  Therefore, it is preferable to perform a cleaning step (not shown) in order to cover the silver with a uniform thickness before the silver plating in the silver coating treatment step S1.

<2-2. Silver coat treatment process>
The silver coating treatment step S <b> 1 is a step of covering the surface of the copper particles as the core material 2 with silver. In the silver coating treatment step S1, since a silver layer is formed on the surface of the copper particles, silver can be coated using a reduction type electroless plating method, a displacement type electroless plating, or the like.

(Reduction type electroless plating method)
In the silver coating treatment step S1, when silver coating is performed by a reduction type electroless plating method, the surface of the copper particles is coated with silver by adding a reducing agent and a silver ion solution to the obtained water slurry. Here, after the reducing agent is added and dispersed in advance in a water slurry containing copper particles, a silver ion solution is continuously added to the water slurry containing the reducing agent and the copper particles, thereby silver on the surface of the copper particles. Is uniformly coated.

  Although various reducing agents can be used as the reducing agent, it is preferably a weak reducing agent that cannot reduce copper complex ions. The reducing organic compound can be used as this weak reducing agent, and for example, carbohydrates, polyvalent carboxylic acids and salts thereof, aldehydes, and the like can be used. Specific examples include glucose (glucose), lactic acid, oxalic acid, tartaric acid, malic acid, malonic acid, glycolic acid, potassium sodium tartrate, formalin and the like.

  In the silver coating treatment step S1, after the reducing agent is added to the water slurry containing copper particles, stirring or the like is performed to sufficiently disperse the reducing agent. Moreover, in order to adjust water slurry to desired pH, it can also add suitably with an acid or an alkali. Further, the dispersion of the reducing organic compound may be promoted by adding a water-soluble organic solvent such as alcohol.

  As the silver ion solution, a known silver plating solution can be used, but a silver nitrate solution is preferable. Moreover, since a silver nitrate solution is easy to form a complex, it is more preferable to add it as an ammoniacal silver nitrate solution. Ammonia used to make an ammoniacal silver nitrate solution can be added to the silver nitrate solution, previously added to the water slurry with a reducing agent and dispersed, or added to the water slurry simultaneously as an ammonia solution separate from the silver nitrate solution, Any method including these combinations may be used.

  You may add a complexing agent to a silver ion solution as needed. The complexing agent is not particularly limited, and N-containing compounds such as sulfites, succinimides, hydantoins, ethylenediamine, and ethylenediaminetetraacetic acid can be used.

  In the silver coating treatment step S1, a silver film having a uniform thickness can be formed by gradually adding a silver ion solution to a water slurry containing copper particles and a reducing agent at a relatively slow rate. . Moreover, in order to improve the uniformity of the thickness of the film, it is more preferable to keep the addition rate constant. Further, the reducing agent or the like previously added to the water slurry may be adjusted to another solution and gradually added together with the silver ion solution.

  Silver-coated copper particles are obtained by filtering, separating and washing the water slurry to which a silver ion solution or the like has been added, followed by drying. These means after filtration are not particularly limited, and known methods may be used.

(Substitutional electroless plating method)
The substitutional electroless plating method uses the difference in ionization tendency between copper and silver and is reduced by electrons generated when copper dissolves in solution and silver ions in solution dissolve. Thus, silver is deposited on the copper surface. Therefore, the substitutional electroless plating solution can be coated with silver if the silver salt, complexing agent, and conductive salt are composed of the main components. A surfactant, brightener, crystal modifier, pH adjuster, suspending agent, stabilizer, etc. are added.

  In the method for producing the silver-coated copper powder according to the present embodiment, a plating solution is not particularly limited, and silver nitrate, silver iodide, silver sulfate, silver formate, as a silver salt in an aqueous slurry in which copper particles are dispersed in water, Silver acetate, silver lactate, etc. can be used. The silver ion concentration in the plating solution is generally 1 g / L to 10 g / L.

  The complexing agent forms a complex with silver ions, and typical examples include citric acid, tartaric acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, N-containing compounds such as ethylenediamine, glycine, hydantoin, pyrrolidone, and succinimide. Hydroxyethylidene diphosphonic acid, aminotrimethylenephosphonic acid, mercaptopropionic acid, thioglycol, thiosemicarbazide and the like can be used. The concentration in the plating solution is generally 10 g / L to 100 g / L.

  As the conductive salt, inorganic acids such as nitric acid, boric acid and phosphoric acid, organic acids such as citric acid, maleic acid, tartaric acid and phthalic acid, or sodium, potassium and ammonium salts thereof can be used. The concentration in the plating solution is generally 5 g / L to 50 g / L.

  The amount of silver coating on the copper particles can be controlled by changing the amount of silver introduced in the substitutional electroless plating solution. Moreover, in order to improve the uniformity of the thickness of the coating, it is preferable to keep the addition rate constant. In the silver coat treatment step S1, after the completion of the reaction, the silver coat copper particle slurry obtained is filtered, separated, washed with water, and dried to obtain silver coat copper particles. The means after the filtration is not particularly limited, and a known method may be used.

<2-3. Surface treatment process>
Next, the surface treatment step S <b> 2 is a step of forming the organic coating layer 4 on the surface of the silver-coated copper particles 5. In the surface treatment step S2 on the silver-coated copper particles 5, specifically, after the silver-coated copper particle slurry generated in the silver-coating step S1 is solid-liquid separated, the cationic surfactant and the dispersant are adsorbed on the surface of the silver-coated copper particles. Let dry.

  In the surface treatment step S2, for example, by performing surface treatment after solid-liquid separation of the silver-coated copper particles 5 from the silver-coated copper particle slurry, by the plating solution residue in the previous step (silver coat treatment step S1), etc. It is possible to prevent the adsorption of the cationic surfactant from being inhibited and to efficiently perform the surface treatment. For this reason, sufficient organic coating layer 4 is formed, and compatibility and dispersibility of a solvent, resin, etc. are ensured.

  The method for solid-liquid separation of the silver-coated copper particle slurry is not particularly limited, and a known method is used. For example, centrifugation, suction filtration, filter press, or the like can be used.

  Specific methods of surface treatment using a cationic surfactant include (1) solid-liquid separation followed by surface treatment with a cationic surfactant and a dispersant, or (2) solid-liquid separation. Thereafter, any of the methods of adding a cationic surfactant and a dispersing agent to the cleaning liquid and performing surface treatment simultaneously with the cleaning during the cleaning that is repeated a plurality of times is preferable. In either case (1) or (2), after the surface treatment with the surfactant and the dispersant, the excess cationic surfactant and dispersant not adsorbed on the surface of the silver-coated copper particles 5 are removed. In order to remove, it is preferable to perform washing.

  When the surface treatment is performed after the solid-liquid separation according to (1) described above, the silver-coated copper particles 5 obtained by solid-liquid separation from the silver-coated copper particle slurry are added to water in which a cationic surfactant and a dispersant are added. The mixture may be added to and stirred, or may be added to and stirred in water containing a cationic surfactant and a dispersant.

  When the surface treatment is performed in the course of repeated cleaning multiple times after the solid-liquid separation according to (2) described above, a cationic surfactant and a dispersing agent may be added to the cleaning liquid so that the cleaning and the surface treatment can be performed simultaneously. Good. In this case, the surface treatment may be performed at any time of cleaning, but since the cationic surfactant has high adsorptivity, the plating solution components such as the complexing agent remaining on the silver-coated copper particles 5 are on the surface. It is preferable that the removal is performed to the extent that the treatment is not affected and the aggregation of the silver-coated copper particles 5 is not progressed, for example, the surface treatment is carried out after washing once.

  In either case of (1) or (2) described above, in order to improve the adsorptivity of the cationic surfactant to the silver-coated copper particles 5, water containing a cationic surfactant and a dispersant is added. Alternatively, the silver-coated copper particles 5 are preferably added to the cleaning liquid and stirred.

  In addition, the apparatus used for washing | cleaning and surface treatment may be an apparatus normally used for washing | cleaning and surface treatment, for example, the reaction tank with a stirrer etc. can be used. Moreover, it is preferable to use the water which does not contain the impurity element harmful | toxic to the silver coat copper particle 1 for washing | cleaning, and it is especially preferable to use a pure water. As the cleaning liquid, in addition to water, an inorganic alkaline substance aqueous solution such as sodium hydroxide, water to which a hydrophilic solvent such as alcohol is added, and combinations thereof can also be used.

  Here, the silver coat copper powder 1 obtained by surface treatment is adjusted so that the internal friction angle is 20 ° or less, the contact angle is 100 ° or more, and the surface SP value is 18 or less. In order to adjust in this way, the above-described 1. As explained for the silver-coated copper powder, the addition amount of the cationic surfactant is preferably in the range of 0.002 mass% to 1.000 mass% with respect to the silver-coated copper particles 4.

  Next, the collection | recovery process which collect | recovers the silver coat copper particles 5 which formed the organic coating layer 4 on the surface can be performed. In this recovery step, after surface treatment and cleaning, the silver-coated copper particles 5 on which the organic coating layer 4 has been formed by solid-liquid separation are recovered. The apparatus used for solid-liquid separation may be a commonly used apparatus, and for example, a centrifuge, a suction filter, a filter press, or the like can be used.

  Next, after the cleaning and the surface treatment are completed, a drying step of evaporating and drying the moisture of the silver-coated copper particles 5 formed with the organic coating layer 4 obtained by solid-liquid separation can be performed. As a drying method, for example, the silver-coated copper particles 5 on which the organic coating layer 4 collected after the cleaning and surface treatment is formed are placed on a stainless steel pad, and a commercially available drying apparatus such as an atmospheric oven or a vacuum dryer is used. What is necessary is just to heat at the temperature of 40 to 80 degreeC. In addition, you may wash again before a drying process.

<2-4. Crushing process>
The crushing step S3 is a step of crushing the silver-coated copper particles 5 that form the organic coating layer 4 obtained in the surface treatment step S2. In the crushing step S3, the silver-coated copper particles 5 that form the organic coating layer 4 specifically obtained in the surface treatment step are used with a high-speed stirrer, and the peripheral speed of the stirring blade is 10 m / second or more and 40 m / second or less. Then, crush it. In the crushing step S3, the silver-coated copper particles 5 on which the dried organic coating layer 4 has been formed are sufficiently crushed to a preferred particle size for paste. In the crushing step S3, classification may be performed to remove fine particles and coarse particles after crushing.

  In the pulverization step S3, the silver-coated copper particles 5 on which the dried organic coating layer 4 is formed are sufficiently weak enough to not damage the organic coating layer 4 formed on the surface, and sufficiently small to a preferred particle size for a silver paste. A silver-coated copper powder 1 is obtained by performing a crushing and classification process of crushing and classifying. The crushing method is not particularly limited as long as it does not damage the organic coating layer 4, and it is preferable to use an apparatus having a weak crushing force such as a jet mill or a high-speed stirrer. A device having a strong crushing force is not preferable because it not only damages the organic coating layer 4 but also deforms the silver-coated copper powder 1. The classification device is not particularly limited, and an airflow classifier, a sieve, or the like can be used.

  The crushing treatment refers to an operation of breaking up the aggregated powder after drying into a state of primary particles or secondary particles before the surface treatment. Various means such as a ball mill, a collision-type airflow pulverizer, an impact-type pulverizer, and a cylindrical high-speed stirrer can be used as pulverization means, but when the energy of pulverization is too weak. Cannot sufficiently unravel the aggregates generated during the wet process or during the drying process, so the internal friction angle cannot be made 20 ° or less. On the other hand, when the energy of crushing is excessively strong, the organic coating layer 4 on the surface of the silver-coated copper powder 1 is damaged or the silver layer 3 is destroyed. As a result, the new surface of the metallic copper is newly exposed on the surface of the silver-coated copper powder 1, so that the hydrophilicity of the surface increases, the contact angle becomes less than 100 °, or the surface SP value becomes larger than 18. Furthermore, the exposed new copper surface may become an active site, reaggregate during storage, and the internal friction angle may increase over time. Here, the new copper surface refers to a surface made of a copper portion of the silver-coated copper powder from which the silver layer has been peeled off by crushing treatment.

  Therefore, in using any crushing machine, crushing conditions should be adjusted while checking parameters such as the internal friction angle, contact angle, and surface SP value. The degree of damage to the organic coating layer 4 on the surface of the silver-coated copper powder 1 is suppressed, that is, the organic coating layer 4 is peeled off so that the silver-coated copper powder 1 is not exposed. It is necessary to add a proper crushing process. Crushing conditions can determine the rotation speed, crushing time, temperature, etc. of a crushing apparatus suitably according to the magnitude | size of the apparatus to crush, the state of the produced silver coat copper powder 1, etc.

  For example, when a high-speed stirrer is used, the conditions vary depending on the capacity of the stirrer, but depending on the amount of silver-coated copper particles 4, the peripheral speed and stirring time of the stirrer are prevented so that the organic coating layer 4 is not damaged. Adjust etc.

  In the method for producing silver-coated copper powder according to the present embodiment, a high-speed stirrer is used and the peripheral speed of the stirring blade is controlled to 10 m / sec or more and 40 m / sec or less. Thereby, the silver coat copper particle 5 after drying can fully be disintegrated to a preferable particle size for paste.

  When the peripheral speed of the stirring blade is less than 10 m / sec, it cannot be sufficiently crushed to a particle size preferable for silver paste. On the other hand, when the peripheral speed of the stirring blade is higher than 40 m / sec, the organic coating layer 4 is peeled off and the silver-coated copper particles 5 are exposed. In any case, it is not preferable when the silver-coated copper particles are made into a paste.

  Moreover, in crushing process S3, it is preferable to control the crushing time which crushes the silver coat copper particle 5 to 10 to 60 minutes with the peripheral speed of a stirring blade using a high-speed stirrer. Thereby, the silver coat copper particle 5 after drying can fully be disintegrated to a preferable particle size for paste.

  When the pulverization time is less than 10 minutes, it is not possible to sufficiently pulverize to a preferred particle size for silver paste. On the other hand, when the pulverization time is longer than 60 minutes, the particle size is already sufficiently pulverized to be preferable for silver paste, which is not preferable in terms of cost.

  In addition, after the crushing treatment, for the purpose of removing aggregated silver-coated copper particle aggregates that have been generated or mixed during the silver-coated copper particle slurry generation step or the crushing / classifying step, an air flow type or a sieve type, etc. It is preferable to perform the classification process.

  By performing the classification treatment after the pulverization treatment, coarse particles and connected particles that could not be crushed can be removed. The classification treatment is suitable when, for example, it is desired to reduce the surface roughness of the conductive film formed using the paste obtained by pasting the silver-coated copper powder 1 of the present invention.

  In the manufacturing method of the silver coat copper powder 1 mentioned above, after forming the organic coating layer 4 in the surface of the silver coat copper powder 1 obtained by the silver particle slurry production | generation process, the new surface of a metal layer is newly added to the silver coat copper particle 5 By pulverizing so as to suppress the formation of a low-hydrophilic silver-coated copper powder 1 having an internal friction angle of 20 ° or less and a contact angle of 100 ° or more. Further, this silver-coated copper powder 1 has a surface SP value of 18 or less. Thereby, in the manufacturing method of the silver coat copper powder 1, when the internal friction angle of the silver coat copper powder 1 is 20 ° or less and the contact angle is 100 ° or more, the wetness of the silver paste with respect to the solvent, resin, etc. Since it is excellent in dispersibility, it has good dispersibility and can be easily pasted to produce a silver paste.

  Accordingly, since the silver-coated copper powder 1 produced by the manufacturing method is uniformly distributed in the silver-coated copper powder paste, the electrical connection is good when a wiring layer or an electrode is formed with the silver-coated copper powder paste. Can be.

[3. Summary]
As mentioned above, the silver coat copper powder 1 which concerns on this Embodiment is the silver coat copper powder 1 by which silver is coat | covered on the surface of a copper particle, Comprising: Silver on the surface of the core material 2 which uses a copper particle, and the core material 2 A silver layer 3 that covers the organic layer 4 and an organic coating layer 4 that is formed by adsorbing a cationic surfactant and a dispersant to the silver layer 3, and the organic coating layer 4 has an internal friction angle of 20 And the contact angle with a 50% by volume aqueous solution of methanol is 100 ° or more.

  The silver-coated copper powder according to the present embodiment is not affected by the residue of the silver plating solution component, is particularly highly compatible with hydrophobic solvents and resins, has excellent dispersibility, and is easily pasted. Is possible. Thereby, in the silver coat copper powder which concerns on this Embodiment, the quality and productivity of the paste using silver coat copper powder can be improved. Further, even after being stored at room temperature after production, the internal friction angle of the silver-coated copper powder hardly changes and maintains 20 ° or less. Therefore, aggregation of the silver coated copper powder due to changes over time is suppressed, and quality control of the paste using the silver coated copper powder becomes easy.

  Moreover, the manufacturing method of the silver coat copper powder which concerns on this Embodiment is a manufacturing method of the silver coat copper powder which used the copper particle as the core material 2, and provided the silver layer 3 on the surface of the core material, Comprising: The surface of the core material 2 The silver coat treatment step S1 for forming the silver layer 3 and the silver coat copper particle slurry obtained in the silver coat treatment step S1 are subjected to surface treatment with a cationic surfactant and a dispersant after solid-liquid separation, and then silver coated copper The surface treatment step S2 for forming the organic coating layer 4 on the surface of the particles 5 and the silver-coated copper particles 5 for forming the organic coating layer 4 obtained in the surface treatment step S2 are mixed using a high-speed stirrer. And crushing step S3 for crushing at 5 m / sec or more and 40 m / sec or less. In the surface treatment step S2, the internal friction angle is 20 ° or less, and the contact angle in a 50% by volume aqueous solution of methanol. Silver coated copper particles 5 so that the The organic coating layer 4 is formed on the surface.

  In the method for producing silver-coated copper powder according to the present embodiment, it is also possible to produce silver-coated copper powder that is highly compatible with hydrophobic solvents, resins, etc., has excellent dispersibility, and can be easily pasted. It becomes possible.

  In addition, silver-coated copper powder pastes can be used to form electrodes for FPD (flat panel display), solar cells, organic EL, etc., wiring for LSI substrates, fine trenches, via holes, and contact holes. It can be used as a wiring forming material such as embedding.

  EXAMPLES The present invention will be described in further detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

<Example 1>
(Washing process)
In Example 1, 100 g of granular atomized copper particles (made by Mekin Metal Powders Co., Ltd.) having an average particle diameter of 7.9 μm were stirred in a 3% aqueous tartaric acid solution for about 1 hour, filtered, washed with water, and 2 L of ion exchange. Dispersed in water.

(Silver coat process)
In Example 1, 5 g of tartaric acid, 5 g of glucose and 50 mL of ethanol were added to the dispersion obtained in the washing step, and 50 mL of 28% ammonia water was further added and stirred.

  Next, in Example 1, an aqueous solution in which 65 g of silver nitrate was dissolved in 4 L of ion-exchanged water, an aqueous solution in which 25 g of glucose, 25 g of tartaric acid and 250 mL of ethanol were dissolved in 750 mL of ion-exchanged water, and 250 mL of 28% ammonia water were each 60 minutes. Over a period of time to obtain a reaction solution. The bath temperature at this time was 25 ° C.

  And in Example 1, after completion | finish of addition, the obtained reaction solution was suction-filtered and the silver coat copper particle 5 was solid-liquid separated. In Example 1, the silver coating amount of the solid-liquid separated silver-coated copper powder 1 was 26.5% by mass with respect to 100% by mass of the silver-coated silver-coated copper powder as a whole.

(Surface treatment process)
Next, in Example 1, the obtained silver-coated copper particles 5 were subjected to a surface treatment. 0.09 g of polyoxyethylene-added quaternary ammonium salt that is a commercially available cationic surfactant as a surface treating agent (trade name Silasol, manufactured by Croda Japan Co., Ltd.) and 1.68 g of a stearic acid emulsion that is a dispersant (Chukyo Oil and Fats) Co., Ltd. (Cerosol 920) was added to 2 L of pure water and stirred to surface-treat the surface of the silver-coated copper particles 5. After this surface treatment, NaOH was added to a concentration of 0.05 mol / L, the mixture was stirred and washed for 15 minutes, and then suction filtered to collect silver-coated copper powder 1.

  Subsequently, before the recovered silver-coated copper powder 1 was dried, the silver-coated copper powder 1 was put into a 0.05 mol / L NaOH aqueous solution, washed with stirring for 15 minutes, and then collected by suction filtration. Thereafter, this washing operation and solid-liquid separation operation by filtration were repeated three times.

  The silver-coated copper particles 5 that form the solid-liquid separated organic coating layer 4 are put into 2 liters of pure water, stirred and filtered, and then the silver-coated copper powder 1 is transferred to a stainless steel pad and is dried in a vacuum dryer at 60. Dry at 10 ° C. for 10 hours.

(Crushing process)
After drying, crushing and classification were performed. For crushing, silver-coated copper particles 5 forming the organic coating layer 4 after drying are put into a high-speed stirrer (manufactured by Nippon Coke Co., Ltd., FM5C / I), and the rotating blades are rotated at a peripheral speed of 15 m / sec. The crushing process was performed by rotating for a minute. Further, the silver-coated copper particles 5 forming the organic coating layer 4 after pulverization are classified using an airflow classifier (Nihon Mining Co., Ltd., EJ-3 type) at a classification point of 20 μm, and then silver-coated. Copper powder 1 was obtained. As a result of measuring the average particle size of the obtained silver-coated copper powder 1 using a laser diffraction scattering method, the particle size (D ₅₀ ) was 12.35 μm.

  As mentioned above, in Example 1, the silver coat copper powder 1 was obtained. About the obtained silver coat copper powder 1, an internal friction angle, a contact angle, and surface SP value were measured, respectively.

For the measurement of the internal friction angle, a powder layer shear force measuring device (manufactured by Nano Seeds Co., Ltd., NS-S300 type) was used. After 18 g of silver-coated copper powder was filled in a stainless steel cell having an inner diameter of 15 mm at room temperature, the indentation load was set to 20 N, and the load was applied at an indentation speed of 0.2 mm / sec. After reaching the set load, side sliding started at a speed of 10 μm / second 100 seconds later. The sampling frequency was 10 Hz. The value obtained by dividing the indentation load at the start of side-sliding by the cell cross-sectional area is the vertical stress σ (N / cm ² ), and the value obtained by dividing the maximum shear force measured after side-sliding by the cell cross-sectional area Was the shear stress τ (N / cm ² ).

  Next, the indentation load set value was 40 N, and the normal stress σ and the shear stress τ were measured in the same manner as when the indentation load set value was 20 N. Furthermore, the set value of indentation load was set to 60N, and the normal stress σ and shear stress τ were measured in the same manner as when the set value of indentation load was set to 20N. As described above, the vertical stress σ obtained on a total of three conditions (setting values of indentation weight: 20N, 40N, 60N) is plotted on the horizontal axis and the shear stress τ is plotted on the vertical axis, and obtained using the least square method. The inclination (°) of the approximate line was taken as the internal friction angle.

  As a result, the internal friction angle of the silver-coated copper powder obtained in Example 1 was 7.0 °. Further, this silver-coated copper powder 1 was put in a container in an air atmosphere and sealed, and stored at room temperature for 1 month. As a result, the internal friction angle of the silver-coated copper powder after one month was 7.7 °.

  The contact angle was measured with a 50% by volume aqueous methanol solution using a contact angle measuring device (Kyowa Interface Science Co., Ltd., CA-X150). At room temperature, the silver-coated copper powder 1 was press-molded with a load of about 1 MPa to obtain a flat test body in which the silver-coated copper powder 1 was compactly filled. The contact angle formed by a 50% by volume methanol aqueous solution was measured on this test specimen. The contact angle of the silver-coated copper powder 1 produced in Example 1 was 109 °.

  The surface SP value was measured by the acetone titration method as follows. Add 50 mL of water to 0.5 g of silver-coated copper powder and slowly drop acetone into the water containing silver-coated copper powder 1 while gently stirring, and the silver-coated copper powder 1 floating on the water surface The end point was when the solution was dispersed and the solution became cloudy. The surface SP value of the acetone aqueous solution calculated from the added volume of acetone at this time was defined as the surface SP of the silver-coated copper powder 1. Here, the surface SP value of the silver coat copper powder 1 produced in Example 1 was 16.6.

Next, paste formation was evaluated using the obtained silver-coated copper powder 1. For evaluation of pasting, first, 9.2 g of silver-coated copper powder and 0.8 g of a vehicle having a weight ratio of 1: 7 epoxy resin (Mitsubishi Chemical Co., Ltd., JER819) and terpineol were weighed in a stainless steel dish. did. At this time, it was observed that the surface of the silver-coated copper powder 1 was quickly wetted by the vehicle. Next, when this was mixed using a metal spatula, mixing and dispersion proceeded easily, and a paste could be formed. Furthermore, this paste was kneaded for 5 minutes at a rotational speed of 2000 rpm using a self-revolving kneading machine (manufactured by Shinky Co., Ltd., ARE-250 type) to obtain a uniform silver-coated copper powder paste. The dispersibility of the obtained silver-coated copper powder paste was evaluated using a grind gauge. As a result, the maximum particle size D _max was as small as 18 μm, and this silver-coated copper powder paste showed excellent dispersibility.

<Example 2>
In Example 2, silver-coated copper powder 1 was prepared in the same manner as in Example 1 except that flaky copper particles were used and the rotating blades of the high-speed stirrer were rotated at a peripheral speed of 28 m / sec. Got. Moreover, the obtained silver coat copper powder 1 was evaluated similarly to Example 1.

  Specifically, in order to obtain flaky copper particles, 5 g of stearic acid was added to 500 g of granular atomized copper particles (manufactured by Mekin Metal Powders) having an average particle diameter of 7.9 μm, and flattened by a ball mill. It was. The ball mill was charged with 5 kg of 3 mm zirconia beads and flattened by rotating for 60 minutes at a rotation speed of 500 rpm.

Then, after obtaining the flaky silver coat copper particle 5 by the same method as Example 1, surface treatment was implemented by the same method as Example 1. As a result, the silver coating amount of the obtained silver coated copper powder was 26.4% by mass with respect to 100% by mass of the silver coated copper powder as a whole. The average particle diameter of the silver-coated copper resulting powder 1, the particle size measured using a laser diffraction scattering method (D ₅₀₎ was 18.39Myuemu. In Example 2, the internal friction angle of the obtained silver-coated copper powder 1 was 10.4 °, and the internal friction angle after storing in a container under an air atmosphere and storing at room temperature for 1 month was It was 10.6 °. Furthermore, in Example 2, the contact angle of the obtained silver-coated copper powder 1 was 108 °, and the surface SP value was 17.3.

Next, using the obtained silver coat copper powder 1, evaluation of pasting similar to Example 1 was performed. It was observed that the surface of the silver-coated copper powder 1 was quickly wetted by the vehicle. When this was mixed using a metal spatula, mixing and dispersion proceeded easily and a paste could be formed. Furthermore, this paste was kneaded with a self-revolving kneader in the same manner as in Example 1 to obtain a uniform silver-coated copper paste. The dispersibility of the obtained silver-coated copper powder paste was evaluated using a grind gauge. As a result, the maximum particle size D _max was as small as 20 μm, and this silver-coated copper powder paste showed excellent dispersibility.

<Example 3>
In Example 3, the silver-coated copper powder 1 was prepared in the same manner as in Example 1 except that flaky copper particles were used and the rotating blades of the high-speed stirrer were rotated at a peripheral speed of 35 m / sec. Got. Moreover, the obtained silver coat copper powder 1 was evaluated similarly to Example 1.

  Specifically, in order to obtain flaky copper particles, 5 g of stearic acid was added to 500 g of granular atomized copper particles (manufactured by Mekin Metal Powders) having an average particle diameter of 7.9 μm, and flattened by a ball mill. It was. The ball mill was charged with 5 kg of 3 mm zirconia beads and flattened by rotating for 60 minutes at a rotation speed of 500 rpm.

Then, after obtaining the flaky silver coat copper particle 5 by the same method as Example 1, surface treatment was implemented by the same method as Example 1. As a result, the silver coating amount of the obtained silver-coated copper powder 1 was 26.2% by mass with respect to 100% by mass of the entire silver-coated copper powder coated with silver. The average particle diameter of the silver-coated copper resulting powder 1, the particle size measured using a laser diffraction scattering method (D ₅₀₎ was 16.21Myuemu. Moreover, in Example 3, the internal friction angle of the obtained silver-coated copper powder 1 was 18.9 °, and the internal friction angle after 1 month storage at room temperature after being sealed in a container in an air atmosphere was 19.1 °. Furthermore, in Example 3, the contact angle of the obtained silver-coated copper powder 1 was 104 °, and the surface SP value was 17.7.

Next, using the obtained silver coat copper powder 1, evaluation of pasting similar to Example 1 was performed. It was observed that the surface of the silver-coated copper powder 1 was quickly wetted by the vehicle. When this was mixed using a metal spatula, mixing and dispersion proceeded easily and a paste could be formed. Furthermore, this paste was kneaded with a self-revolving kneader in the same manner as in Example 1 to obtain a uniform silver-coated copper paste. The dispersibility of the obtained silver-coated copper powder paste was evaluated using a grind gauge. As a result, the maximum particle size D _max was as small as 22 μm, and this silver-coated copper powder paste showed excellent dispersibility.

<Example 4>
In Example 4, 0.06 g of beef tallow diamine oleate (trade name Rheomix TDO, manufactured by Lion Corporation) was used instead of 0.09 g of polyoxyethylene-added quaternary ammonium salt (trade name Silasol). A silver-coated copper powder was obtained in the same manner as in Example 1. Moreover, the obtained silver coat copper powder 1 was evaluated similarly to Example 1.

The silver coating amount of the obtained silver-coated copper powder 1 was 26.3% by mass with respect to 100% by mass of the entire silver-coated silver-coated copper powder. The average particle diameter of the silver-coated copper resulting powder 1, the particle size measured using a laser diffraction scattering method (D ₅₀₎ was 12.15Myuemu. Moreover, in Example 4, the internal friction angle of the obtained silver-coated copper powder 1 is 15.7 °, and the internal friction angle after storing in a container in an air atmosphere and storing it at room temperature for 1 month is It was 16.0 °. Furthermore, in Example 4, the contact angle of the obtained silver coat copper powder 1 was 109 degrees, and the surface SP value was 17.1.

Next, paste formation was evaluated in the same manner as in Example 1 using the obtained silver-coated copper powder 1. It was observed that the surface of the silver-coated copper powder 1 was quickly wetted by the vehicle. When this was mixed using a metal spatula, mixing and dispersion proceeded easily and a paste could be formed. Further, this paste was kneaded in a self-revolving kneader in the same manner as in Example 1 to obtain a uniform silver-coated copper powder paste. The dispersibility of the obtained silver-coated copper powder paste was evaluated using a grind gauge. As a result, the maximum particle size D _max was 28 μm, and this silver-coated copper powder paste showed good dispersibility.

<Comparative Example 1>
In Comparative Example 1, silver-coated copper powder 1 was obtained in the same manner as in Example 1 except that the rotating blades of the high-speed stirrer were rotated at a peripheral speed of 42 m / sec. Moreover, the obtained silver coat copper powder 1 was evaluated similarly to Example 1.

In the comparative example 1, the silver coating amount of the obtained silver coat copper powder 1 was 26.4 mass% with respect to 100 mass% of the silver coat copper powder 1 whole coated with silver. The average particle diameter of the silver-coated copper powder obtained, the particle size measured using a laser diffraction scattering method (D ₅₀₎ was 8.72Myuemu. Moreover, in Comparative Example 1, the internal friction angle of the obtained silver-coated copper powder 1 is 20.9 °, which is considerably higher than those of Examples 1 to 4, and sealed in an air atmosphere in a container. The internal friction angle after 1 month storage at room temperature was also 21.3 °. Furthermore, in Comparative Example 1, the contact angle of the obtained silver-coated copper powder 1 was 86 °, and the surface SP value was 18.8.

  Next, paste formation was evaluated in the same manner as in Example 1 using the obtained silver-coated copper powder 1. Wetting by the vehicle on the surface of the silver-coated copper powder 1 was hardly observed. Moreover, when this was stirred using a metal spatula, it remained in a large clay state and could not be made into a paste.

Further, this silver-coated copper powder 1 was kneaded in a self-revolving kneader in the same manner as in Example 1 to obtain a paste. The dispersibility of the obtained silver-coated copper powder paste was evaluated using a grind gauge. As a result, the maximum particle size D _max was 40 μm, and this silver-coated copper powder paste had poor dispersibility.

<Comparative example 2>
In Comparative Example 2, a silver-coated copper powder was obtained in the same manner as in Example 2 except that the rotating blades of the high-speed stirrer were rotated at a peripheral speed of 7 m / sec. Moreover, the obtained silver coat copper powder 1 was evaluated similarly to Example 1.

In the comparative example 2, the silver coating amount of the obtained silver coat copper powder 1 was 26.5 mass% with respect to 100 mass% of the silver coat copper powder 1 whole coated with silver. The average particle diameter of the silver-coated copper powder obtained, the particle size measured using a laser diffraction scattering method (D ₅₀₎ was 13.52Myuemu. Moreover, in Comparative Example 2, the internal friction angle of the obtained silver-coated copper powder 1 is 25.8 °, which is considerably higher than those of Examples 1 to 4, and sealed in a container in an air atmosphere. The internal friction angle after 1 month storage at room temperature was also 26.1 °. Furthermore, in Comparative Example 2, the obtained silver-coated copper powder 1 had a contact angle of 111 ° and a surface SP value of 17.5.

  Next, using the obtained silver coat copper powder 1, evaluation of pasting similar to Example 1 was performed. Wetting by the vehicle on the surface of the silver-coated copper powder 1 was hardly observed. Moreover, when this was stirred using a metal spatula, it remained in a large clay state and could not be made into a paste.

Further, this silver-coated copper powder 1 was kneaded in a self-revolving kneader in the same manner as in Example 1 to obtain a paste. The dispersibility of the obtained silver-coated copper powder paste was evaluated using a grind gauge. As a result, the maximum particle size D _max was as large as 43 μm and the dispersibility was poor.

<Comparative Example 3>
In Comparative Example 3, a silver-coated copper powder 1 was obtained in the same manner as in Example 1 except that 0.09 g of a polyoxyethylene-added quaternary ammonium salt (trade name Silasol, manufactured by Crodal Japan Co., Ltd.) was not added. It was. Moreover, the obtained silver coat copper powder 1 was evaluated similarly to Example 1.

In the comparative example 3, the silver coating amount of the obtained silver coat copper powder 1 was 26.6 mass% with respect to 100 mass% of the silver coat copper powder 1 whole coated with silver. The average particle diameter of the silver-coated copper resulting powder 1, the particle size measured using a laser diffraction scattering method (D ₅₀₎ was 12.51Myuemu. Moreover, in Comparative Example 3, the internal friction angle of the obtained silver-coated copper powder 1 was 27.9 °, and the internal friction angle after storing in a container under an air atmosphere and storing at room temperature for 1 month was It was 30.4 °. Furthermore, in Comparative Example 3, the contact angle of the obtained silver-coated copper powder 1 was 115 °, and the surface SP value was 16.9.

Next, in Comparative Example 3, evaluation of pasting as in Example 1 was performed using the obtained silver-coated copper powder 1. It was observed that the surface of the silver-coated copper powder 1 was quickly wetted by the vehicle. When this was mixed using a metal spatula, mixing and dispersion proceeded easily and a paste could be formed. Further, in Comparative Example 3, this paste was kneaded with a self-revolving kneader in the same manner as in Example 1 to obtain a paste. The dispersibility of the obtained silver-coated copper powder paste was evaluated using a grind gauge. As a result, the maximum particle size D _max was 40 μm, and this silver-coated copper powder paste had poor dispersibility.

<Consideration based on Examples>
As mentioned above, even if Examples 1-4 and Comparative Examples 1-3 are the silver powder produced by the same method, Example 1 which fully disintegrated in the grade which does not damage the film formed on the surface of silver coat copper powder -4, the internal friction angle is 20 ° or less and the contact angle in a 50% by volume methanol aqueous solution is 100 ° or more, and the compatibility with the vehicle is good and the dispersibility. The silver coat copper powder 1 which was excellent in was obtained. Moreover, in Examples 1-4, the surface SP value by the acetone titration method was 18 or less. Furthermore, in Examples 1 to 4, even after the silver-coated copper powder was stored at room temperature for 1 month, the internal friction angle was 20 ° or less, and aggregation was suppressed.

  On the other hand, in Comparative Example 1, because the crushing conditions were too severe, the organic coating layer formed on the surface of the silver-coated copper powder 1 was damaged, the internal friction angle was larger than 20 °, and the contact angle was also 100 °. Became smaller. Furthermore, the surface SP value was also larger than 18.

  Moreover, in the comparative example 2, since the crushing conditions were low and the aggregate could not be sufficiently loosened, the internal friction angle was considerably large as 25.8 °. Thereby, in the comparative example 1 and the comparative example 2, compatibility with a vehicle was low and the dispersibility of the silver coat copper powder 1 worsened.

  In Comparative Example 3, since the fatty acid was used instead of the cationic surfactant, the internal friction angle was larger than 20 °. In Comparative Example 3, when the obtained silver-coated copper powder was made into a paste, the compatibility with the vehicle was low, and the dispersibility of the silver-coated copper powder 1 was poor.

  Further, in Comparative Example 3, as compared with Examples 1 to 3, even when the silver-coated copper powder was stored at room temperature for 1 month, the internal friction angle was larger than 20 ° and was aggregated.

1 silver coat copper powder, 2 core material, 3 silver layer, 4 organic coating layer, 5 silver coat copper particle, S1 silver coat treatment process, S2 surface treatment process, S3 crushing process

Claims (10)

A silver-coated copper powder in which silver is coated on the surface of the copper particles,
A core material using the copper particles;
A silver layer covering the silver on the surface of the core material;
The silver layer has an organic coating layer formed by adsorbing a cationic surfactant and a dispersant,
Silver-coated copper powder, wherein the organic coating layer has an internal friction angle of 20 ° or less and a contact angle with a 50% by volume aqueous methanol solution of 100 ° or more.   The silver-coated copper powder according to claim 1, wherein the surface SP value by an acetone titration method is 18 or less.   The core material has any one of a spherical shape, a flake shape, a dendritic shape, a disc shape, and an ellipsoid shape, and has an average particle diameter of 0.1 μm to 20 μm. The silver coat copper powder of 2.   The amount of silver coated with respect to 100% by mass of the entire silver-coated silver-coated copper powder is 0.5% by mass to 50% by mass, according to any one of claims 1 to 3. The silver coat copper powder of description.   The silver-coated copper powder according to any one of claims 1 to 4, wherein the cationic surfactant is a quaternary ammonium salt type.   The silver-coated copper powder according to any one of claims 1 to 5, wherein the dispersant is a fatty acid or a salt thereof. Using copper particles as a core material, a method for producing a silver-coated copper powder comprising a silver layer on the surface of the core material,
A silver coating treatment step for forming a silver layer on the surface of the core material;
A surface treatment step of solid-liquid separating the silver-coated copper particle slurry obtained in the silver coating treatment step and then surface-treating with a cationic surfactant and a dispersant to form an organic coating layer on the surface of the silver-coated copper particles; ,
A crushing step of crushing the silver-coated copper particles forming the organic coating layer obtained in the surface treatment step with a high speed stirrer at a peripheral speed of the stirring blade of 10 m / second to 40 m / second; Have
In the surface treatment step, the organic coating layer is formed on the surface of the silver-coated copper particles so that the internal friction angle is 20 ° or less and the contact angle in a 50% by volume aqueous methanol solution is 100 ° or more. The manufacturing method of the silver coat copper powder characterized by the above-mentioned.   The silver coat according to claim 7, wherein in the surface treatment step, an organic coating layer is formed on the surface of the silver-coated copper particles by adding 0.01% to 3.00% by mass of the dispersant. A method for producing copper powder.   The method for producing silver-coated copper powder according to claim 7 or 8, wherein in the crushing step, the silver-coated copper particles are crushed in a crushing time of 10 minutes to 60 minutes.   The method for producing a silver-coated copper powder according to any one of claims 7 to 9, further comprising a washing step of washing the copper particles as a pre-step of the silver coating treatment step.