TW201920697A - Silver powder and method for producing same - Google Patents

Abstract

There are provided a silver powder, which contains a small amount of carbon and which is difficult to aggregate. While a molten metal, which is prepared by melting silver to which 40 ppm or more of copper is added, is allowed to drop, a high-pressure water is sprayed onto the molten metal to rapidly cool and solidify the molten metal to produce a silver powder which contains 40 ppm or more of copper, 0.1 % by weight or less of carbon and 0.1 % by weight or less of oxygen and wherein the particle diameter (D50 diameter) corresponding to 50% of accumulation in volume-based cumulative distribution of the silver powder, which is measured by a laser diffraction particle size analyzer, is in the range of from 1 micrometer to 15 micrometers, the average particle diameter (SEM diameter) of a single particle being in the range of from 1 micrometer to 8 micrometers when it is measured by a field emission scanning electron microscope (SEM), the ratio (SEM diameter / D50 diameter) of the SEM diameter to the D50 diameter being in the range of from 0.3 to 1.0.

Description

Silver powder and its manufacturing method

FIELD OF THE INVENTION The present invention relates to silver powder and its manufacturing method, and particularly to silver powder suitable for conductive paste materials and its manufacturing method.

BACKGROUND OF THE INVENTION Conventionally, as electrodes for forming solar cells, electronic parts using low-temperature co-fired ceramics (LTCC), multilayer ceramic electronic parts such as multilayer ceramic inductors (MLCI), multilayer ceramic capacitors or multilayer ceramic inductors, etc. For conductive paste materials such as external electrodes, metal powders such as silver powder are used.

As for the silver powder used as this conductive paste material, a method for producing silver powder has been proposed, in which a reducing agent is added to an aqueous reaction system containing silver ions in the presence of copper and other particles to reduce and precipitate the silver particles ( (See Patent Document 1 as an example).

In addition, a method for producing silver powder is proposed, in which an aggregation inhibitor such as stearate is added to a silver aqueous solution such as silver nitrate, and then a reducing agent is added to reduce and precipitate silver particles (see Patent Document 2 for an example).

Prior Art Literature Patent Literature Patent Literature 1: Japanese Patent Laid-Open No. 2009-235474 (Paragraph No. 0012-0014)
Patent Document 2: Japanese Patent Laid-Open No. 2013-14790 (paragraph number 0023~0027)]

SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION However, such as the method of manufacturing silver powder as described in Patent Documents 1 to 2, the method of manufacturing silver powder by the wet reduction method, during the manufacturing process, the particles of silver powder are ingested as impurities. Carbon compounds. Therefore, if the silver powder produced by this method is used as a material for firing a conductive paste, and the firing conductive paste is applied to a substrate and fired to form a conductive film, the firing may When gas such as carbon dioxide is generated from the carbon component, there is a problem that the conductive film cracks due to the gas, so that the adhesion between the conductive film and the substrate becomes poor.

In order to solve the above problem, as for a method of manufacturing silver powder with a very low impurity content such as carbon at a low price, there is known a method in which a molten liquid in which silver has been melted is dropped while spraying high-pressure water to make the molten liquid A method of producing silver powder by rapid cooling and solidification, a so-called water atomization method.

However, the silver powder produced by the silver powder manufacturing method using the water atomization method in the past is easy to agglomerate and make the secondary particle size larger. If the silver powder thus aggregated is used as a conductive paste material, it is difficult to form a smooth surface. Thin conductive film.

In recent years, due to the miniaturization of internal electrodes of electronic components such as multilayer ceramic inductors (MLCI), silver powder with a small particle size is particularly needed for silver powder used for conductive paste, but if the particle size of the silver powder becomes smaller, the silver powder is easier Agglutination.

Therefore, in view of the above-mentioned conventional problems, an object of the present invention is to provide a silver powder having a small carbon content and difficult to aggregate and a method for manufacturing the same.

Means for Solving the Problems The inventors deliberately studied to solve the above-mentioned problems. As a result, they found that the molten liquid obtained by melting silver containing copper at 40 ppm or more was dropped and sprayed with high-pressure water to rapidly cool and solidify the molten liquid. A silver powder containing 40 ppm or more of copper and having a carbon content of 0.1% by mass or less can be produced, and a silver powder having a small carbon content and difficult to aggregate can be produced, and the present invention has been completed.

That is, the silver powder of the present invention is characterized by having a copper content of 40 ppm or more and a carbon content of 0.1% by mass or less.

The copper content in the silver powder is preferably 40 to 10000 ppm. Furthermore, the volume-based cumulative 50% particle size (D ₅₀ particle size) obtained by measuring the silver powder with a laser diffraction particle size distribution measuring device is preferably 1 to 15 μm, obtained by observing the silver powder with a field emission scanning electron microscope The ratio of the average particle diameter (SEM particle diameter) of the monomer particles to the cumulative 50% particle diameter (D ₅₀ particle diameter) of the silver powder (SEM particle diameter/D ₅₀ particle diameter) is preferably 0.3 to 1.0. In addition, the ratio of the tap density of the silver powder to the cumulative 50% particle size (D ₅₀ particle size) (tap density/D ₅₀ particle size) is preferably 0.45 to 3.0 g/(cm ³ ·μm). In addition, the oxygen content in the silver powder is preferably 0.1% by mass or less. Furthermore, the BET specific surface area of the silver powder is preferably 0.1 to 1.0 m ² /g, and the tap density is preferably 2 to 6 g/cm ³ .

In addition, the method for producing the silver powder of the present invention is characterized in that the molten liquid obtained by melting silver containing 40 ppm or more of copper is dropped while spraying high-pressure water to rapidly cool and solidify the molten liquid. In the method of manufacturing the silver powder, the copper content in the melt is preferably 40 to 10000 ppm.

In addition, the conductive paste of the present invention is characterized in that the above-mentioned silver powder is dispersed in the organic component.

Furthermore, the method for manufacturing a conductive film of the present invention is characterized in that the conductive paste is applied to a substrate and then fired to produce a conductive film.

Effects of the Invention With the present invention, it is possible to produce silver powder having a small carbon content and difficult to aggregate.

[Mode for carrying out the invention] The embodiment of the silver powder of the present invention has a copper content of 40 ppm or more and a carbon content of 0.1% by mass or less.

The copper content in the silver powder (from the viewpoint of preventing aggregation of the silver powder) is preferably 40 ppm or more, and from the viewpoint of improving the oxidation resistance and conductivity of the silver powder, it is preferably 40 to 10000 ppm, and 40 to 2000 ppm is better, 40~800ppm is better, 230~750ppm is the best.

The carbon content in the silver powder is 0.1% by mass or less, and preferably 0.03% by mass or less, more preferably 0.007% by mass or less. If a firing conductive paste using such a low carbon content silver powder as a material is applied to a substrate and then fired to form a conductive film, the amount of gas such as carbon dioxide generated from the carbon component during firing is small, which is conductive The film is hard to crack due to gas, and a conductive film with good adhesion to the substrate can be formed.

In addition, the oxygen content in the silver powder is preferably 0.1% by mass or less, and 0.01 to 0.07% by mass is more preferable. If the oxygen content in the silver powder is generally low as described, it can be fully sintered to form a highly conductive conductive film.

The cumulative 50% particle size (D ₅₀ particle size) obtained by measuring the silver powder with a laser diffraction particle size distribution measuring device (by the HELOS method) based on volume is preferably 1 to 15 μm. If the silver powder is used as In the case of forming conductive paste materials such as internal electrodes of more miniaturized electronic parts, 1 to 8 μm is more preferable, and 1.2 to 7 μm is optimal. In addition, the average particle size (SEM particle size) of the monomer particles obtained by observing the silver powder using a field emission scanning electron microscope (SEM), if the silver powder is used as a conductive paste for forming an internal electrode of a more compact electronic component, etc. In the case of materials, 1~8μm is better, and 1~5μm is better, and 1.2~4μm is the best. Furthermore, the ratio of the average particle diameter (SEM particle diameter) of the monomer particles obtained by observing the silver powder with a field emission scanning electron microscope to the cumulative 50% particle diameter (D ₅₀ particle diameter) of the silver powder (SEM particle diameter/D ₅₀ Particle size), preferably 0.3~1.0, and 0.35~1.0 is better, 0.5~1.0 is better, 0.65~1.0 is the best. It can be said that the larger the ratio (SEM particle diameter/D ₅₀ particle diameter) (primary particle diameter/secondary particle diameter), the less aggregation of the silver powder.

In addition, the BET specific surface area of the silver powder is preferably 0.1 to 1.0 m ² /g, and 0.2 to 0.8 m ² /g is better, and 0.3 to 0.5 m ² /g is the best. In addition, in order to improve the filling of the silver powder and form a conductive film with good conductivity when using silver powder as the conductive paste material to form the conductive film, the tap density of the silver powder is preferably 2 to 6 g/cm ³ and 2.5 to 5.5 g /cm ^{3 is} better, 3.5~5.5g/cm ^{3 is the} best. Furthermore, in order to improve the filling of the silver powder and form a conductive film with good conductivity when using silver powder as the conductive paste material to form the conductive film, the tap density of the silver powder relative to the cumulative 50% particle size (D ₅₀ particle size) The ratio (tap density/D ₅₀ particle size) should be 0.45~3.0g/(cm ³ ·μm), and 0.8~2.8g/(cm ³ ·μm) is better, 1.1~2.5g/(cm ³ ·μm) )optimal.

In addition, the shape of the silver powder may be any of various granular shapes such as a spherical shape or a platelet shape, or may be an indefinite shape with different shapes.

The embodiment of the above-mentioned silver powder can be produced by the embodiment of the method for producing silver powder of the present invention.

The embodiment of the production method of the silver powder of the present invention is to add 40 ppm or more of copper (preferably in the form of copper monomer or Ag-Cu alloy) to silver (preferably 40 to 10000 ppm, more preferably 40 to 2000 ppm, especially It should be 40~800ppm, the best is 230~750ppm) and melted (preferably 300~720°C higher than the melting point of copper of about 962°C). The melt falls at the same time (preferably in atmospheric environment or (hydrogen , Carbon monoxide, argon, nitrogen, etc.) in a non-oxidizing gas environment and under a water pressure of 70 to 400 MPa (more preferably 90 to 280 MPa)) spray high pressure water (of pure water or alkaline water with a pH of 8 to 12) to make The melt is rapidly cooled and solidified.

If by spraying high-pressure water, the so-called water atomization method, by adding traces of silver (such as 40ppm or more, preferably 40 ~ 10000ppm, more preferably 40 ~ 2000ppm, especially preferably 40 ~ 800ppm, the best is 230 ~750ppm) of molten copper to produce silver powder, silver powder with small particle size, low carbon content and difficult to agglomerate can be obtained.

In addition, when the silver powder is produced from the melt by the water atomization method, the average particle size of the silver powder can be adjusted by adjusting the temperature of the melt and the pressure of high-pressure water. For example, the average particle size of silver powder can be reduced by increasing the temperature of the melt or the pressure of high-pressure water.

In addition, when silver powder is produced from the melt by the water atomization method, the slurry obtained by spraying high pressure water while dropping the melt to rapidly cool and solidify the melt can be solid-liquid separated, and the resulting solid can be dried to obtain silver powder. In addition, if necessary, the solids obtained by the solid-liquid separation can be washed with water before drying, or can be broken or classified after drying to adjust the particle size.

When the embodiment of the silver powder of the present invention is used as a material for (sintered conductive paste, etc.) conductive paste, the silver powder can be dispersed in (saturated aliphatic hydrocarbons, unsaturated aliphatic hydrocarbons, ketones, aromatic Conductive pastes are produced from organic components such as hydrocarbons, glycols, esters, alcohols, etc.) organic solvents or (ethyl cellulose, acrylic resins, etc.) binder resins. In addition, if necessary, a glass frit, an inorganic oxide, a dispersant, etc. may be added to the conductive paste.

From the viewpoint of the manufacturing cost of the conductive paste and the conductivity of the conductive film, the silver powder content in the conductive paste is preferably 5 to 98% by mass, and more preferably 70 to 95% by mass. In addition, the silver powder in the conductive paste can be mixed with one or more other metal powders (metal powder such as alloy powder of silver and tin, tin powder, etc.). The metal powder may be a metal powder having a shape or particle size different from the embodiment of the silver powder of the present invention. In order to fire a conductive paste to form a thin conductive film, the cumulative 50% particle size (D ₅₀ particle size) of the metal powder measured by a laser diffraction particle size distribution measuring device based on volume is preferably 0.5 ~20μm. Moreover, the content of the metal powder in the conductive paste is preferably 1 to 94% by mass, and more preferably 4 to 29% by mass. In addition, the total content of silver powder and metal powder in the conductive paste is preferably 60 to 99% by mass. In addition, considering the dispersibility of the silver powder in the conductive paste and the appropriate viscosity of the conductive paste, the content of the organic solvent in the conductive paste is preferably 0.8 to 20% by mass, and 0.8 to 15% by mass is better. This organic solvent can be used by mixing two or more kinds. In addition, from the viewpoint of the dispersibility of silver powder in the conductive paste and the conductivity of the conductive paste, the content of the binder resin in the conductive paste is preferably 0.1 to 10% by mass, and more preferably 0.1 to 6% by mass. The binder resin can be used by mixing two or more kinds. In addition, from the viewpoint of the sinterability of the conductive paste, the glass frit content in the conductive paste is preferably 0.1 to 20% by mass, and more preferably 0.1 to 10% by mass. The glass frit can be used by mixing two or more kinds.

Such a conductive paste can be produced, for example, by measuring each component and placing it in a predetermined container, pre-kneading it with a mortar mill, universal mixer, kneader, etc. Mixing. In addition, if necessary, an organic solvent can be added later to adjust the viscosity. In addition, after mixing glass frit or inorganic oxide with organic solvent or binder resin to reduce the particle size, finally add silver powder for formal mixing.

The conductive paste can be applied on the substrate (ceramic substrate or dielectric layer, etc.) to a predetermined pattern shape by dipping or printing (metal stencil printing, screen printing, inkjet printing, etc.) and then fired. To form a conductive film. When the conductive paste is applied by dipping, the substrate is immersed in the conductive paste to form a coating film, and then the coating film is fired, and then unnecessary parts of the resulting conductive film are removed to be applied to the substrate A conductive film with a predetermined pattern shape is formed thereon.

The firing of the conductive paste coated on the substrate can be carried out in a non-oxidizing gas environment such as nitrogen, argon, hydrogen, carbon monoxide, etc., but the silver powder is difficult to oxidize, so it is suitable for atmospheric environment due to cost considerations get on. In addition, the firing temperature of the conductive paste is preferably about 600 to 1000°C, and more preferably about 700 to 900°C. In addition, before firing the conductive paste, vacuum drying or the like may be used for pre-drying to remove volatile components such as organic solvents in the conductive paste. In addition, in the case where the conductive paste contains a binder resin, it is appropriate to heat the conductive paste at a low temperature of 250 to 400°C before firing, as a binder removal step to reduce the content of the binder resin.

EXAMPLES Hereinafter, examples of the silver powder of the present invention and its production method will be described in detail.

Example 1
In an atmospheric environment, 23.96 kg of silver beads with a purity of 99.99% by mass and 6.04 kg of Ag-Cu alloy (containing 228 ppm of copper) were heated to 1600°C to melt into a molten solution (a silver molten solution containing 46 ppm of copper) and the molten solution was removed from Feed the trough under the tribe, at the same time in the atmospheric environment by the water atomization device at a water pressure of 150MPa and a water volume of 160L/min, spray alkaline water (addition of caustic soda 157.55g to pure water 21.6m ³ ( pH 10.7)) to rapidly cool and solidify the molten liquid, and then solid-liquid separation of the resulting slurry, and washing and drying the solid matter to obtain silver powder (containing trace copper).

The monomer particle size (primary particle size) of the silver powder obtained in the above manner was observed with a field emission scanning electron microscope (SEM) (S-4700 manufactured by Hitachi High-Technologies Corporation) at a magnification of 5000 times, and then from The average particle size (SEM particle size) of the monomer particles is determined from the average value of the Feret's diameter of any 30 particles. As a result, the SEM particle size (primary particle size) of the silver powder was 2.35 μm. As for the aggregated particle size (secondary particle size) of silver powder, a laser diffraction particle size distribution measuring device (HELOS particle size distribution measuring device (HELOS & RODOS (air flow dispersion mode)) manufactured by SYMPATEC) was used at a dispersion pressure of 5 bar Next, the cumulative 50% particle size (D ₅₀ particle size) based on volume is measured, and then the cumulative 50% particle size (D ₅₀ particle size) of the silver powder is 6.0 μm. In addition, the ratio (primary particle diameter/secondary particle diameter) of the SEM particle diameter (primary particle diameter) to the cumulative 50% particle diameter (D ₅₀ particle diameter) (secondary particle diameter) was calculated to be 0.39.

Furthermore, the composition analysis of the silver powder was performed using an inductively coupled plasma (ICP) emission spectrometer (SPS3520V manufactured by Hitachi High-Tech Science Corporation), and then the copper content in the silver powder was ±10% of the copper content in the melt Within range.

In addition, the carbon content in the silver powder was measured using a carbon/sulfur analyzer (EMIA-920V2 manufactured by Horiba Manufacturing Co., Ltd.), and the carbon content was 0.004% by mass, and an oxygen, nitrogen, and hydrogen analyzer (Horiba) was used. The EMGA-920 produced by the company was used to measure the oxygen content and found that the oxygen content was 0.040% by mass.

Furthermore, using a BET specific surface area measuring instrument (Macsorb manufactured by MOUNTECH Co., Ltd.), nitrogen gas was passed through the measuring instrument at 105° C. for 20 minutes for degassing, and then a mixed gas of nitrogen and helium (N ₂ : 30% by volume, He: 70% by volume), at the same time, the BET specific surface area of the silver powder was measured by the BET single-point method, and then the BET specific surface area was 0.34 m ² /g.

Furthermore, regarding the tap density (TAP) of silver powder, in the same manner as the method described in Japanese Patent Laid-Open No. 2007-263860, a cylindrical mold with a bottom of 6 mm in inner diameter × 11.9 mm in height is filled with silver powder up to the volume 80% to form a silver powder layer, and uniformly apply a pressure of 0.160 N/m ² on the top of the silver powder layer, compress the silver powder under this pressure until it can no longer be denser, measure the height of the silver powder layer, and determine the height of the silver powder layer The measured value and the weight of the silver powder filled to obtain the density of the silver powder. As a result, the tap density was 3.0 g/cm ³ . In addition, the ratio of the tap density (TAP) of the silver powder to the cumulative 50% particle size (D ₅₀ particle size) (TAP/D ₅₀ particle size) was 0.50 g/(cm ³ ·μm).

Example 2
It was prepared in the same manner as in Example 1 (with trace copper), except that a molten solution of 25 kg of silver beads and 15 kg of Ag-Cu alloy (containing 581 ppm of copper) was used (a silver molten solution containing 218 ppm of copper). Silver powder.

Calculate the SEM particle size (primary particle size) of the silver powder produced according to the above method, and measure the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size), and calculate the SEM particle size (primary particle size) ) Relative to the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size) ratio (SEM particle size/D ₅₀ particle size) (primary particle size/secondary particle size), and then: SEM of silver powder The particle size (primary particle size) is 2.34 μm, the cumulative 50% particle size (D ₅₀ particle size) is 4.1 μm, and the SEM particle size/D ₅₀ particle size (primary particle size/secondary particle size) is 0.57.

In addition, the composition analysis of the silver powder was performed in the same manner as in Example 1, the carbon content and oxygen content in the silver powder were measured, and the BET specific surface area and tap density (TAP) of the silver powder were calculated, and the tap density of the silver powder was calculated (TAP) relative to the cumulative 50% particle size (D ₅₀ particle size) ratio (TAP/D ₅₀ particle size), and then obtained: the copper content in the silver powder is within ±10% of the copper content in the melt, The carbon content is 0.002% by mass, the oxygen content is 0.041% by mass, the BET specific surface area is 0.36 m ² /g, the tap density is 4.1 g/cm ³ , and the tap density (TAP) of the silver powder is relative to the cumulative 50% particle size The ratio (D ₅₀ particle size) (TAP/D ₅₀ particle size) is 1.00 g/(cm ³ ·μm).

Example 3
It was prepared in the same manner as in Example 1 (with trace copper), except for using a molten solution of 24kg of silver beads and 16kg of Ag-Cu alloy containing 595ppm of copper (a silver molten solution containing 238ppm of copper). Silver powder.

Calculate the SEM particle size (primary particle size) of the silver powder produced according to the above method, and measure the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size), and calculate the SEM particle size (primary particle size) ) Relative to the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size) ratio (SEM particle size/D ₅₀ particle size) (primary particle size/secondary particle size), and then: SEM of silver powder The particle diameter (primary particle diameter) is 2.19 μm, the cumulative 50% particle diameter (D ₅₀ particle diameter) is 2.9 μm, and the SEM particle diameter/D ₅₀ particle diameter (primary particle diameter/secondary particle diameter) is 0.75.

In addition, the composition analysis of the silver powder was performed in the same manner as in Example 1, the carbon content and oxygen content in the silver powder were measured, and the BET specific surface area and tap density (TAP) of the silver powder were calculated, and the tap density of the silver powder was calculated (TAP) relative to the cumulative 50% particle size (D ₅₀ particle size) ratio (TAP/D ₅₀ particle size), and then obtained: the copper content in the silver powder is within ±10% of the copper content in the melt, The carbon content is 0.004% by mass, the oxygen content is 0.051% by mass, the BET specific surface area is 0.42m ² /g, the tap density is 4.2g/cm ³ , and the tap density (TAP) of the silver powder is relative to the cumulative 50% particle size The ratio (D ₅₀ particle size) (TAP/D ₅₀ particle size) is 1.45 g/(cm ³ ·μm).

Example 4
It was prepared in the same manner as in Example 1 (with trace copper), except for using a molten solution of 25 kg of silver beads and 15 kg of Ag-Cu alloy containing 675 ppm of copper (a silver molten solution containing 253 ppm of copper). Silver powder.

Calculate the SEM particle size (primary particle size) of the silver powder produced according to the above method, and measure the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size), and calculate the SEM particle size (primary particle size) ) Relative to the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size) ratio (SEM particle size/D ₅₀ particle size) (primary particle size/secondary particle size), and then: SEM of silver powder The particle diameter (primary particle diameter) was 2.51 μm, the cumulative 50% particle diameter (D ₅₀ particle diameter) was 3.1 μm, and the SEM particle diameter/D ₅₀ particle diameter (primary particle diameter/secondary particle diameter) was 0.81.

In addition, the composition analysis of the silver powder was performed in the same manner as in Example 1, the carbon content and oxygen content in the silver powder were measured, and the BET specific surface area and tap density (TAP) of the silver powder were calculated, and the tap density of the silver powder was calculated (TAP) relative to the cumulative 50% particle size (D ₅₀ particle size) ratio (TAP/D ₅₀ particle size), and then obtained: the copper content in the silver powder is within ±10% of the copper content in the melt, The carbon content is 0.003% by mass, the oxygen content is 0.036% by mass, the BET specific surface area is 0.36 m ² /g, the tap density is 5.0 g/cm ³ , and the tap density (TAP) of the silver powder is relative to the cumulative 50% particle size The ratio (D ₅₀ particle size) (TAP/D ₅₀ particle size) is 1.61 g/(cm ³ ·μm).

Example 5
It was prepared in the same manner as in Example 1 (except for trace copper), except for using a molten solution of 18.62 kg of silver beads and 11.38 kg of Ag-Cu alloy (containing 975 ppm of copper) (a silver molten solution containing 370 ppm of copper). Of) silver powder.

Calculate the SEM particle size (primary particle size) of the silver powder produced according to the above method, and measure the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size), and calculate the SEM particle size (primary particle size) ) Relative to the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size) ratio (SEM particle size/D ₅₀ particle size) (primary particle size/secondary particle size), and then: SEM of silver powder The particle diameter (primary particle diameter) was 2.54 μm, the cumulative 50% particle diameter (D ₅₀ particle diameter) was 2.8 μm, and the SEM particle diameter/D ₅₀ particle diameter (primary particle diameter/secondary particle diameter) was 0.90.

In addition, the composition analysis of the silver powder was performed in the same manner as in Example 1, the carbon content and oxygen content in the silver powder were measured, and the BET specific surface area and tap density (TAP) of the silver powder were calculated, and the tap density of the silver powder was calculated (TAP) relative to the cumulative 50% particle size (D ₅₀ particle size) ratio (TAP/D ₅₀ particle size), and then obtained: the copper content in the silver powder is within ±10% of the copper content in the melt, The carbon content is 0.004% by mass, the oxygen content is 0.049% by mass, the BET specific surface area is 0.37m ² /g, the tap density is 4.7g/cm ³ , and the tap density (TAP) of the silver powder is relative to the cumulative 50% particle size The ratio (D ₅₀ particle size) (TAP/D ₅₀ particle size) was 1.68 g/(cm ³ ·μm).

Example 6
Except for using 6.27kg of melted silver beads and 2.43kg of Ag-Cu alloy (containing 1343ppm of copper) (a silver melting solution containing 375ppm of copper), it was prepared in the same manner as in Example 1 (containing trace copper Of) silver powder.

Calculate the SEM particle size (primary particle size) of the silver powder produced according to the above method, and measure the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size), and calculate the SEM particle size (primary particle size) ) Relative to the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size) ratio (SEM particle size/D ₅₀ particle size) (primary particle size/secondary particle size), and then: SEM of silver powder The particle diameter (primary particle diameter) was 2.83 μm, the cumulative 50% particle diameter (D ₅₀ particle diameter) was 3.1 μm, and the SEM particle diameter/D ₅₀ particle diameter (primary particle diameter/secondary particle diameter) was 0.91.

In addition, the composition analysis of the silver powder was performed in the same manner as in Example 1, the carbon content and oxygen content in the silver powder were measured, and the BET specific surface area and tap density (TAP) of the silver powder were calculated, and the tap density of the silver powder was calculated (TAP) relative to the cumulative 50% particle size (D ₅₀ particle size) ratio (TAP/D ₅₀ particle size), and then obtained: the copper content in the silver powder is within ±10% of the copper content in the melt, The carbon content is 0.006% by mass, the oxygen content is 0.069% by mass, the BET specific surface area is 0.35 m ² /g, the tap density is 4.7 g/cm ³ , and the tap density (TAP) of the silver powder is relative to the cumulative 50% particle size ( The ratio of D ₅₀ particle size) (TAP/D ₅₀ particle size) is 1.52 g/(cm ³ ·μm).

Example 7
It was prepared in the same manner as in Example 1 (with trace copper), except that 29.79 kg of melted silver beads and 10.21 kg of Ag-Cu alloy (containing 1508 ppm of copper) were used (containing 385 ppm of silver melt). Of) silver powder.

Calculate the SEM particle size (primary particle size) of the silver powder produced according to the above method, and measure the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size), and calculate the SEM particle size (primary particle size) ) Relative to the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size) ratio (SEM particle size/D ₅₀ particle size) (primary particle size/secondary particle size), and then: SEM of silver powder The particle size (primary particle size) was 2.57 μm, the cumulative 50% particle size (D ₅₀ particle size) was 2.9 μm, and the SEM particle size/D ₅₀ particle size (primary particle size/secondary particle size) was 0.89.

In addition, the composition analysis of the silver powder was performed in the same manner as in Example 1, the carbon content and oxygen content in the silver powder were measured, and the BET specific surface area and tap density (TAP) of the silver powder were calculated, and the tap density of the silver powder was calculated (TAP) relative to the cumulative 50% particle size (D ₅₀ particle size) ratio (TAP/D ₅₀ particle size), and then obtained: the copper content in the silver powder is within ±10% of the copper content in the melt, The carbon content is 0.002% by mass, the oxygen content is 0.046% by mass, the BET specific surface area is 0.36 m ² /g, the tap density is 4.3 g/cm ³ , and the tap density (TAP) of the silver powder is relative to the cumulative 50% particle size The ratio (D ₅₀ particle size) (TAP/D ₅₀ particle size) is 1.48 g/(cm ³ ·μm).

Example 8
It was prepared in the same manner as in Example 1 (except for using a molten solution of molten silver beads 39.97 kg and 0.031 kg of Ag-Cu alloy containing 28% by mass of copper) (a silver molten solution containing 218 ppm of copper). Copper 220ppm) silver powder.

Calculate the SEM particle size (primary particle size) of the silver powder produced according to the above method, and measure the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size), and calculate the SEM particle size (primary particle size) ) Relative to the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size) ratio (SEM particle size/D ₅₀ particle size) (primary particle size/secondary particle size), and then: SEM of silver powder The particle diameter (primary particle diameter) is 2.33 μm, the cumulative 50% particle diameter (D ₅₀ particle diameter) is 4.3 μm, and the SEM particle diameter/D ₅₀ particle diameter (primary particle diameter/secondary particle diameter) is 0.54.

In addition, the composition analysis of the silver powder was performed in the same manner as in Example 1, the carbon content and oxygen content in the silver powder were measured, and the BET specific surface area and tap density (TAP) of the silver powder were calculated, and the tap density of the silver powder was calculated (TAP) relative to the cumulative 50% particle size (D ₅₀ particle size) ratio (TAP/D ₅₀ particle size), and then it is obtained: the copper content in the silver powder is 220 ppm, the carbon content is 0.005 mass%, and the oxygen content is 0.046 Mass%, BET specific surface area is 0.34m ² /g, tap density is 3.7g/cm ³ , and the ratio of tap density (TAP) of silver powder to cumulative 50% particle size (D ₅₀ particle size) (TAP/ D ₅₀ particle size) is 0.84 g/(cm ³ ·μm).

Example 9
Except for using 31.79kg of molten silver beads and 8.21kg of Ag-Cu alloy (containing 1252ppm of copper) (a silver melting solution containing 257ppm of copper), it was prepared in the same manner as in Example 1 (containing 270ppm of copper) Of) silver powder.

Calculate the SEM particle size (primary particle size) of the silver powder produced according to the above method, and measure the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size), and calculate the SEM particle size (primary particle size) ) Relative to the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size) ratio (SEM particle size/D ₅₀ particle size) (primary particle size/secondary particle size), and then: SEM of silver powder The particle diameter (primary particle diameter) is 2.60 μm, the cumulative 50% particle diameter (D ₅₀ particle diameter) is 2.9 μm, and the SEM particle diameter/D ₅₀ particle diameter (primary particle diameter/secondary particle diameter) is 0.89.

In addition, the composition analysis of the silver powder was performed in the same manner as in Example 1, the carbon content and oxygen content in the silver powder were measured, and the BET specific surface area and tap density (TAP) of the silver powder were calculated, and the tap density of the silver powder was calculated (TAP) relative to the cumulative 50% particle size (D ₅₀ particle size) ratio (TAP/D ₅₀ particle size), and then obtained: the copper content in the silver powder is 270ppm, the carbon content is 0.001% by mass, and the oxygen content is 0.042 Mass%, BET specific surface area is 0.37m ² /g, tap density is 4.7g/cm ³ , and the ratio of tap density (TAP) of silver powder to cumulative 50% particle size (D ₅₀ particle size) (TAP/ D ₅₀ particle size) is 1.60 g/(cm ³ ·μm).

Example 10
It was prepared in the same manner as in Example 1 (with a copper content of 310 ppm) except that a molten solution (silver solution containing 303 ppm of copper) containing 48.00 kg of melted silver beads and 32.00 kg of Ag-Cu alloy containing 757 ppm of copper was used. Of) silver powder.

Calculate the SEM particle size (primary particle size) of the silver powder produced according to the above method, and measure the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size), and calculate the SEM particle size (primary particle size) ) Relative to the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size) ratio (SEM particle size/D ₅₀ particle size) (primary particle size/secondary particle size), and then: SEM of silver powder The particle diameter (primary particle diameter) is 2.73 μm, the cumulative 50% particle diameter (D ₅₀ particle diameter) is 3.6 μm, and the SEM particle diameter/D ₅₀ particle diameter (primary particle diameter/secondary particle diameter) is 0.76.

In addition, the composition analysis of the silver powder was performed in the same manner as in Example 1, the carbon content and oxygen content in the silver powder were measured, and the BET specific surface area and tap density (TAP) of the silver powder were calculated, and the tap density of the silver powder was calculated (TAP) relative to the cumulative 50% particle size (D ₅₀ particle size) ratio (TAP/D ₅₀ particle size), and then it is obtained: the copper content in the silver powder is 310 ppm, the carbon content is 0.003 mass%, and the oxygen content is 0.042 Mass%, BET specific surface area is 0.35m ² /g, tap density is 4.1g/cm ³ , and the ratio of tap density (TAP) of silver powder to cumulative 50% particle size (D ₅₀ particle size) (TAP/ D ₅₀ particle size) was 1.14 g/(cm ³ ·μm).

Example 11
It was prepared in the same manner as in Example 1 (with 360 ppm copper content), except that 20.69 kg of molten silver beads and 19.31 kg of Ag-Cu alloy (containing 723 ppm of copper) were used (a silver molten solution containing 349 ppm of copper). Of) silver powder.

Calculate the SEM particle size (primary particle size) of the silver powder produced according to the above method, and measure the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size), and calculate the SEM particle size (primary particle size) ) Relative to the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size) ratio (SEM particle size/D ₅₀ particle size) (primary particle size/secondary particle size), and then: SEM of silver powder The particle diameter (primary particle diameter) was 3.15 μm, the cumulative 50% particle diameter (D ₅₀ particle diameter) was 3.3 μm, and the SEM particle diameter/D ₅₀ particle diameter (primary particle diameter/secondary particle diameter) was 0.97.

In addition, the composition analysis of the silver powder was performed in the same manner as in Example 1, the carbon content and oxygen content in the silver powder were measured, and the BET specific surface area and tap density (TAP) of the silver powder were calculated, and the tap density of the silver powder was calculated (TAP) relative to the cumulative 50% particle size (D ₅₀ particle size) ratio (TAP/D ₅₀ particle size), and then obtained: the copper content in the silver powder is 360ppm, the carbon content is 0.003% by mass, and the oxygen content is 0.043 Mass%, BET specific surface area is 0.38m ² /g, tap density is 3.8g/cm ³ , and the ratio of tap density of silver powder (TAP) to cumulative 50% particle size (D ₅₀ particle size) (TAP/ D ₅₀ particle size) is 1.16 g/(cm ³ ·μm).

Example 12
It was prepared in the same manner as in Example 1 (620 ppm containing copper), except that 6.00 kg of melted silver beads and 14.00 kg of Ag-Cu alloy (containing 800 ppm of copper) were used (a silver melt containing 560 ppm of copper). Of) silver powder.

Calculate the SEM particle size (primary particle size) of the silver powder produced according to the above method, and measure the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size), and calculate the SEM particle size (primary particle size) ) Relative to the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size) ratio (SEM particle size/D ₅₀ particle size) (primary particle size/secondary particle size), and then: SEM of silver powder The particle diameter (primary particle diameter) was 2.32 μm, the cumulative 50% particle diameter (D ₅₀ particle diameter) was 2.8 μm, and the SEM particle diameter/D ₅₀ particle diameter (primary particle diameter/secondary particle diameter) was 0.84.

In addition, the composition analysis of the silver powder was performed in the same manner as in Example 1, the carbon content and oxygen content in the silver powder were measured, and the BET specific surface area and tap density (TAP) of the silver powder were calculated, and the tap density of the silver powder was calculated (TAP) relative to the cumulative 50% particle size (D ₅₀ particle size) ratio (TAP/D ₅₀ particle size), and then obtained: the copper content in the silver powder is 620ppm, the carbon content is 0.003% by mass, and the oxygen content is 0.057 Mass%, BET specific surface area is 0.38m ² /g, tap density is 4.4g/cm ³ , the ratio of tap density of silver powder (TAP) to cumulative 50% particle size (D ₅₀ particle size) (TAP/D ₅₀ particle size) is 1.59g/(cm ³ ·μm).

In the comparative example, silver powder was prepared in the same manner as in Example 1, except that 5 kg of melted silver beads was used.

Calculate the SEM particle size (primary particle size) of the silver powder produced according to the above method, and measure the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size), and calculate the SEM particle size (primary particle size) ) Relative to the cumulative 50% particle size (D ₅₀ particle size) (secondary particle size) ratio (SEM particle size/D ₅₀ particle size) (primary particle size/secondary particle size), and then: SEM of silver powder The particle diameter (primary particle diameter) was 2.33 μm, the cumulative 50% particle diameter (D ₅₀ particle diameter) was 9.6 μm, and the SEM particle diameter/D ₅₀ particle diameter (primary particle diameter/secondary particle diameter) was 0.24.

In addition, the composition analysis of the silver powder was performed in the same manner as in Example 1, the carbon content and oxygen content in the silver powder were measured, and the BET specific surface area and tap density (TAP) of the silver powder were calculated, and the tap density of the silver powder was calculated (TAP) relative to the cumulative 50% particle size (D ₅₀ particle size) ratio (TAP/D ₅₀ particle size), and then obtained: The resulting silver powder is silver powder without Cu, the carbon content is 0.004% by mass, the oxygen content is 0.038% by mass, BET specific surface area is 0.35m ² /g, tap density is 2.3g/cm ³ , and the ratio of tap density (TAP) of silver powder to cumulative 50% particle size (D ⁵⁰ particle size) (TAP /D ₅₀ particle size) is 0.24 g/(cm ³ ·μm).

Table 1 and Table 2 show the amounts and characteristics of copper in the silver powder raw materials of these examples and comparative examples. In addition, a field emission scanning electron microscope (FE-SEM) photograph of the silver powder produced in Examples 8 to 12 was observed at 5000 times as shown in FIGS. 1 to 5.

Table 1

Table 2

INDUSTRIAL APPLICABILITY The silver powder of the present invention can be used as a material for firing a conductive paste to produce a highly conductive conductive film for forming solar cell electrodes and electronic parts using low temperature co-fired ceramics (LTCC) Or internal electrodes of multilayer ceramic electronic parts such as multilayer ceramic inductors, external electrodes of multilayer ceramic capacitors or multilayer ceramic inductors, etc.

The one shown in FIG. 1 is a field emission scanning electron microscope (FE-SEM) photograph of the silver powder obtained in Example 8 at 5000 times.

The one shown in FIG. 2 is a FE-SEM photograph of the silver powder obtained in Example 9 at 5000 times.

The one shown in FIG. 3 is an FE-SEM photograph of the silver powder obtained in Example 10 at 5000 times.

The one shown in FIG. 4 is a FE-SEM photograph of the silver powder obtained in Example 11 at 5000 times.

The one shown in FIG. 5 is a FE-SEM photograph of the silver powder obtained in Example 12 at 5000 times.

Claims (12)

A silver powder characterized by having a copper content of 40 ppm or more and a carbon content of 0.1% by mass or less. If the silver powder of claim 1, the copper content in the aforementioned silver powder is 40 to 10000 ppm. For the silver powder according to claim 1, its cumulative 50% particle size measured by a laser diffraction particle size distribution measuring device based on volume is 1 to 15 μm. The silver powder according to claim 3, wherein the ratio of the average particle size (SEM particle size) of the monomer particles obtained by observing the aforementioned silver powder with a field emission scanning electron microscope to the cumulative 50% particle size (D ₅₀ particle size) of the aforementioned silver powder ( SEM particle size/D ₅₀ particle size) is 0.3 to 1.0. The silver powder according to claim 3, wherein the ratio of the tap density of the aforementioned silver powder to the cumulative 50% particle size (D ₅₀ particle size) (tap density/D ₅₀ particle size) is 0.45 to 3.0 g/(cm ³ ·μm ). If the silver powder of claim 1, the oxygen content in the aforementioned silver powder is 0.1% by mass or less. For the silver powder of claim 1, the BET specific surface area of the aforementioned silver powder is 0.1 to 1.0 m ² /g. If the silver powder of claim 1, the tap density of the aforementioned silver powder is 2~6g/cm ³ . A method for manufacturing silver powder is characterized in that the molten liquid obtained by melting silver containing copper at 40 ppm or more is dropped and high-pressure water is sprayed to rapidly cool and solidify the molten liquid. The method for manufacturing silver powder according to claim 9, wherein the copper content in the melt is 40 to 10000 ppm. A conductive paste characterized in that silver powder as described in claim 1 is dispersed in an organic component. A method for manufacturing a conductive film, characterized in that the conductive paste according to claim 11 is applied to a substrate and then fired to produce a conductive film.