TW201538757A - Copper powder - Google Patents

Abstract

The present invention provides a novel copper powder capable of ensuring a low powder resistance and excellent conductivity while the copper power is formed of fine particles. Provided is a copper powder, which is characterized by: the volume accumulation particle size D50 determined by laser diffraction scattering particle size detection device is 0.20 [mu]m to 0.70 [mu]m, and the ratio of a diameter of crystallite to the D50(diameter of crystallite/D50) is 0.15 to 0.60 ([mu]m/[mu]m).

Description

Copper powder

The present invention relates to a copper powder which can be used as a conductive material for various purposes, for example, a conductive paste used for forming a circuit, forming an external electrode of a ceramic capacitor, or the like, and copper powder as a conductive filler can be used.

As a method of forming an electrode and an electric circuit of an electronic component or the like, it is known that a conductive paste in which a copper powder as a conductive material is dispersed into a paste is printed on a substrate, and the paste is fired or cooked and hardened to form a circuit. The method.

Such a conductive paste is a fluid composition in which a conductive filler is dispersed in a vehicle liquid composed of a resin-based binder and a solvent, and is widely used in formation of a circuit, formation of an external electrode of a ceramic capacitor, and the like.

The conductive paste is of the following type: a resin-cured type which is cured by a resin to ensure that the conductive filler is pressure-bonded and turned on; and a calcination type in which the organic component is volatilized by firing and the conductive filler is sintered. Be sure to turn on.

The resin-curable conductive paste of the former usually contains a conductive filler composed of a metal powder; and thermosetting property by an epoxy resin or the like In the paste composition of the organic binder composed of a resin, the thermosetting resin and the conductive filler are simultaneously hardened and shrunk by applying heat, and the conductive filler is pressure-bonded by the resin to be in contact with each other, thereby ensuring conduction. Sex. Such a resin-curable conductive paste can be used in a printed wiring board, a heat-resistant resin substrate, or the like because it can be treated in a relatively low-temperature region from 100 ° C to 200 ° C at the same time and has less heat damage.

On the other hand, the latter calcined conductive paste is a paste-like composition obtained by dispersing a conductive filler composed of a metal powder and a glass frit in an organic vehicle, and calcining at 500 to 900 ° C. The organic medium liquid is volatilized, and the conductive material can be sintered to ensure conductivity. At this time, the glass frit has a function of causing the conductive film to function next to the substrate, and the organic vehicle serves as an organic liquid medium for enabling printing of the metal powder and the glass frit.

Since the calcination type conductive paste has a high calcination temperature, it cannot be used for a printed wiring board or a resin material. However, since the metal is integrated by sintering, it is possible to reduce the resistance, and for example, it can be used for an external electrode of a multilayer ceramic capacitor. .

In any of the resin-curable conductive paste and the high-temperature calcined conductive paste, copper powder has been widely used as a conductive filler in the past. Since copper powder is not only inexpensive, but also does not easily migrate and has excellent solder resistance, the conductive paste using copper powder is gradually being used.

In addition, in recent years, as the fine pitch of electrical circuits and the like progresses, the copper powder for the conductive paste is required to be micronized.

For the micronization of copper powder, for example, Patent Document 1 discloses A method for reducing a copper hydroxide in a liquid to a metallic copper particle using a reducing agent, and using the ruthenium or osmium compound as a reducing agent, while performing the reduction reaction in the presence of an antifoaming agent, and by reducing A surface treatment agent may be added before or after the reaction or in the middle of the reaction to obtain a fine copper powder having a short diameter and a long diameter of less than 100 nm.

Patent Document 2 discloses a method for producing a copper powder which is a fine particle and a uniform particle by a wet reduction method, and discloses a method for producing a copper powder, comprising the steps of: reacting an aqueous solution containing a copper ion with an alkali solution; The formed copper hydroxide slurry is subjected to a first reduction treatment by adding a reducing agent to the copper hydroxide slurry to form a cuprous oxide slurry; and the cuprous oxide slurry is allowed to stand to precipitate the cuprous oxide particles. The upper clear liquid is removed, and the cuprous oxide particles are washed by adding water to form a washed cuprous oxide slurry; and a reducing agent is added to the washed cuprous oxide slurry to obtain a second reduction treatment. Copper powder; the copper powder production method is characterized in that the first reduction treatment is carried out in a copper hydroxide slurry, and an aqueous ammonia solution containing a hydrazine as a reducing agent and a pH adjuster is added.

In Patent Document 3, even if fine particles are used, it is possible to adjust the sintering initiation temperature to a higher copper powder, and to disclose a copper powder which contains copper powder for conductive paste of Al (aluminum) and P (phosphorus). It is characterized in that the Al concentration is 0.01 atm% or more and less than 0.80 atm%, and the D50 of the volume-based particle size distribution measured by the laser diffraction scattering type particle size distribution measurement is 0.1 μm to 10 μm.

Patent Document 4 discloses a method of steaming a raw material powder (metal powder) by adding it to a high-frequency plasma flame. The surface treatment is carried out in the middle of production, and the dispersibility of the copper powder in the solution is improved by surface treatment of the pyroelectric slurry to obtain copper powder having a particle diameter of several nm to several tens of nm.

Prior technical literature Patent literature

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2004-211108

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2007-254846

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2012-67327

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2008-138284

In recent years, in the field of electrical circuits and the like, with the progress of fine pitch in recent years, as described above, copper powder for conductive paste is gradually required to be micronized.

However, since the copper powder is more micronized to the tens of nm level, surface oxidation becomes remarkable and the powder resistance tends to be high, and the conductivity is deteriorated when the paste is printed/cured to form a circuit, and the electrical conductivity is deteriorated. Components that require continuity of reliability cannot be used as a component of circuit materials.

Accordingly, the present invention provides a novel copper powder which is capable of ensuring low powder resistance and excellent electrical conductivity even with particulate copper powder.

The invention provides a copper powder characterized by using a volumetric cumulative particle determined by a laser diffraction scattering particle size distribution measuring device The diameter D50 is from 0.20 μm to 0.70 μm, and the ratio of the crystallite diameter to the D50 (crystallite diameter/D50) is from 0.15 to 0.60 (μm/μm).

The copper powder of the present invention is characterized in that although the D50 is a micronized copper powder of 0.20 μm to 0.70 μm, the ratio of the crystallite diameter to the D50 (crystallite diameter/D50) is 0.15 to 0.60 (μm/μm), micro The crystal diameter is large. Therefore, the copper powder proposed by the present invention has a low powder resistance and excellent electrical conductivity even in the case of the fine copper powder, and the coating film formed using the conductive paste of the copper powder can also obtain excellent electrical conductivity. Sex.

Further, the copper powder proposed by the present invention has excellent dispersibility, and the coating film of the conductive paste using the copper powder of the present invention has excellent smoothness.

Therefore, the copper powder for conductive paste used in the conductor circuit of a printed wiring board, the electrode of a laminated ceramic capacitor, etc. can be used suitably, for example.

1‧‧‧ Plasma device

2‧‧‧Powder supply device

3‧‧‧Reaction room

4‧‧‧DC Plasma Torch

5‧‧‧Recycling tank

6‧‧‧Powder supply nozzle

7‧‧‧ gas supply device

8‧‧‧ Pressure adjustment device

Fig. 1 is a view conceptually showing an example of an apparatus for producing a copper powder of the present invention.

Fig. 2 is a photograph of the plasma flame generated in Example 3 taken from the side where the flame width was the widest.

Fig. 3 is a photograph of the plasma flame generated in Comparative Example 1 taken from the side where the flame width was the widest.

Fig. 4 is a photomicrograph of the copper powder obtained in Example 3.

Next, an example of a form for carrying out the invention will be described. However, the present invention is not limited by the embodiments described below.

<this copper powder>

The copper powder of the present embodiment (hereinafter referred to as "the present copper powder") is a copper powder characterized in that the volume cumulative particle diameter D50 measured by a laser diffraction scattering type particle size distribution measuring apparatus is 0.20 μm. 0.70 μm, and the ratio of the crystallite diameter to the D50 (crystallet diameter/D50) was 0.15 to 0.60 (μm/μm).

(D50)

The D50 of the copper powder, that is, the D50 of the volume-based particle size distribution measured by the laser diffraction scattering particle size distribution measurement method is preferably 0.20 μm to 0.70 μm as described above. When the D50 of the copper powder is 0.70 μm or less, a fine line can be easily formed when the paste is printed, and if it is 0.20 μm or more, high aspect ratio printing can be easily performed.

Therefore, from this viewpoint, the D50 of the present copper powder is preferably 0.20 μm to 0.70 μm, more preferably 0.21 μm or more or 0.65 μm or less, more preferably 0.22 μm or more or 0.55 μm or less, and 0.25 μm or less. The above or 0.40 μm or less is further more preferable.

(D90)

The D90 of the copper powder, that is, the volume reference particle size D90 measured by the laser diffraction scattering type particle size distribution measuring apparatus, is preferably 0.35 μm to 12.0 μm. When the D90 of the copper powder is 0.35 μm or more, since the influence of the surface energy of the particles is small, it is easy to prevent the condensation when it becomes a paste. When the concentration is 12.0 μm or less, since the coarse particles are small, the filling rate can be increased and the powder resistance can be lowered.

Therefore, from this viewpoint, the D90 of the present copper powder is preferably 0.35 μm to 12.0 μm, more preferably 0.38 μm or more or 9.00 μm or less, and more preferably 0.40 μm or more or 2.00 μm or less, and further preferably Further preferably 0.50 μm or more or 0.70 μm or less.

(D10)

The D10 of the copper powder, that is, the volume cumulative particle diameter D10 measured by a laser diffraction scattering type particle size distribution measuring apparatus, is preferably 0.08 μm to 0.30 μm. When the D10 of the present copper powder is 0.08 μm or more, it is possible to prevent aggregation of the fine particles when kneading as a conductive paste, and when it is 0.30 μm or less, a conductive paste having a low particle filling property and low electrical resistance can be obtained.

Therefore, from this viewpoint, the D10 of the present copper powder is preferably 0.08 μm to 0.30 μm, particularly 0.09 μm or more or 0.28 μm or less, and more preferably 0.10 μm or more or 0.26 μm or less, and 0.12 μm or less thereof. The above or 0.20 μm or less is further more preferable.

((D90-D10)/D50)

In the present copper powder, ((D90-D10)/D50), that is, the relationship of the above D10, D50, and D90 is preferably ((D90-D10)/D50) = 1.0 to 7.0.

Since ((D90-D10)/D50) is an index indicating the sharpness of the particle size distribution, the particle size distribution is sufficiently sharp in the range of 1.0 to 7.0, and the dimensional deviation can be controlled when the conductive paste is printed to form a circuit, so Enjoy the benefits of obtaining a wiring board with excellent impedance control.

From this point of view, in the copper powder ((D90-D10) / D50), is 1.0 It is preferable to be 7.0, and it is preferably 1.1 or more or 6.0 or less, and more preferably 1.2 or more or 3.0 or less, and further preferably 1.3 or more or 2.0 or less.

In the present copper powder, in order to adjust ((D90-D10)/D50) to a range of 1.0 to 7.0, as described later, when a DC hot plasma (referred to as "DC plasma") device is used to heat and spray the raw material copper powder, It is preferred to use a mixed gas of argon and nitrogen as the plasma gas. However, the method is not limited.

(crystallite diameter)

The crystallite diameter of the present copper powder is preferably 0.15 to 0.60 (μm/μm) with respect to the ratio of the crystallite diameter of the aforementioned D50 (crystallet diameter/D50). When the crystallite diameter/D50 of the copper powder is 0.15 (μm/μm) or more, the powder resistance can be further lowered, and when it is 0.60 (μm/μm) or less, the particle shape can be kept substantially spherical.

Therefore, from this viewpoint, the crystallite diameter/D50 of the present copper powder is preferably 0.15 to 0.60 (μm/μm), particularly preferably 0.20 (μm/μm) or more or 0.58 (μm/μm) or less, wherein Further preferably, it is 0.22 (μm/μm) or more or 0.55 (μm/μm) or less.

In addition, the "crystallite diameter" is obtained by analyzing a diffraction pattern obtained by diffraction of powder X-rays and calculating a half-width of a diffraction angle peak of a crystal plane calculated by Scherrer's formula. The average of the crystallite diameters.

Further, the ratio of the crystallite diameter of the present copper powder to the average particle diameter (Dsem) of the primary particles (crystallite diameter/Dsem) is preferably 0.10 to 0.70 (μm/μm). When the crystallite diameter/Dsem of the copper powder is 0.10 (μm/μm) or more, the powder resistance can be further lowered to 0.70 (μm/μm) or less. At the time, the particle shape system can maintain a substantially spherical shape.

Therefore, from this viewpoint, the crystallite diameter/Dsem of the present copper powder is preferably 0.10 to 0.70 (μm/μm), and more preferably 0.15 (μm/μm) or more or 0.60 (μm/μm) or less. More preferably, it is 0.20 (μm/μm) or more or 0.50 (μm/μm) or less, and further preferably 0.30 (μm/μm) or more or 0.40 (μm/μm) or less.

In addition, the "average particle diameter of primary particles" is obtained by scanning a copper powder with a scanning electron microscope (magnification: 10,000 times or 30,000 times), and the primary particle diameter of each particle is measured by a ball, and the obtained ball is converted once. The average of the particle sizes.

In order to prepare the particle size and the crystallite diameter of the present copper powder as described above, a mixed gas of argon and nitrogen is used as the electric power when the raw material copper powder is heated by using a direct current thermal plasma (referred to as "DC plasma") device as will be described later. At the same time as the slurry gas, the plasma flame is used as a laminar flow state and the adjustment is made to be wide and long. However, it is not limited by this method.

In general, when the copper powder is microparticulated, the crystallite diameter becomes small, but as in the above-described DC plasma method, as described above, the crystallite diameter can be increased.

(oxygen amount)

Regarding the present copper powder, the ratio of the oxygen amount (O amount) to the surface area (SSA) is preferably 0.10 to 0.40 (wt%.g/m ² ).

When the ratio of the amount of oxygen (O amount) to the surface area (SSA) is 0.10 (wt%.g/m ² ) or more, the particle shape can be maintained to be substantially spherical, and on the other hand, it is 0.40 (wt%.g/m). ² ) In the following, since the oxygen concentration on the surface of the particles can be lowered, the powder resistance can be kept lower.

Therefore, from this point of view, the ratio of the oxygen amount (O amount) to the surface area (SSA) of the present copper powder is preferably 0.10 to 0.40 (wt%.g/m ² ), wherein 0.15 (wt%.g/ m ² ) or more or 0.35 (wt%.g/m ² ) or less is preferable, and further preferably 0.17 (wt%.g/m ² ) or more or 0.30 (wt%·g/m ² ) or less.

In the present copper powder, in order to adjust the ratio of the oxygen amount (O amount) to the surface area (SSA) in the above range, as described above, when the raw material copper powder is heated and sprayed using a DC plasma apparatus, a mixed gas of argon and nitrogen is used. As the plasma gas, it can be adjusted in such a manner that the plasma flame is laminar and becomes wider and longer. However, it is not limited by this method.

(particle shape)

Regarding the present copper powder, the particle shape is not particularly limited. However, from the viewpoint of dispersibility, it is preferred to have a spherical shape or a large spherical shape. For example, when the copper powder is observed by an electron microscope (for example, 85,000 times), most of the copper powder particles are preferably spherical or slightly spherical. More specifically, 50% by number or more of the copper powder particles constituting the copper powder, of which 80% or more, more preferably 90% or more, and 95% or more of them (including 100% by number) ) is spherical or roughly spherical.

When the copper powder containing spherical or substantially spherical copper powder particles is contained in this manner, particularly excellent dispersibility can be obtained, and for example, by mixing with the flaky powder, the denseness can be further improved.

Here, the term "greatly spherical" means not a completely spherical shape, but can be recognized as a shape of a ball.

In order to adjust the particle shape of the present copper powder as described above, when the raw material copper powder is heated and sprayed using a DC plasma apparatus as described above, argon is used. When the mixed gas of nitrogen and the nitrogen gas are used as the plasma gas, the plasma flame is used as a laminar flow state and adjusted to be wide and long. However, it is not limited by this method.

Further, in the present copper powder, it is also preferable to process the spherical particles or the substantially spherical particles into fragmentary particles, and it is also preferable that the spherical shape or the substantially spherical particles are mixed with the fragmented particles.

(ingredient)

The copper powder may contain Si, P, Ni, Ti, Fe, Co, Cr, Mg, Mn, Mo, W, Ta, In, Zr, Nb, B, Ge, Sn, Zn, Bi in addition to Cu. At least one or more elemental components. By including these, various characteristics required for the conductive paste can be adjusted, for example, the melting point is lowered to improve the sinterability and the like.

(pressing powder resistance)

The powder compaction resistance of the copper powder is 1.0×10 ^-1 Ω. Below cm, which is 5.0 × 10 ^-2 Ω. The following is better than cm, which is 1.0 × 10 ^-2 Ω. Below cm is better. When the powder pressure of the copper powder is within such a range, the contact resistance between the particles can be kept low, so that it can be excellent in electrical conductivity when the conductive paste is formed.

In order to adjust the powder pressure resistance of the present copper powder as described above, when a copper plasma powder is heated and sprayed using a DC plasma apparatus as described above, a mixed gas of argon and nitrogen is used as a plasma gas, and a plasma flame is used as a layer. The flow state is adjusted to be wide and long. However, it is not limited by this method.

<Method>

Next, a preferred method of producing the present copper powder will be described.

When the copper powder is heated and sprayed by using a DC plasma device, a mixed gas of argon and nitrogen is used as the plasma gas, and the plasma flame is laminar and adjusted to be wide and long. Manufacturing. However, it is not limited by this method.

Here, whether the plasma flame is in a laminar flow state, and when the plasma flame is observed from the side where the flame width is the widest, the aspect ratio of the flame length to the flame width (hereinafter, the flame aspect ratio) is 3 When it is judged that the flame aspect ratio is 3 or more, it can be judged as a laminar flow state, and if it is less than 3, it can be judged as a turbulent flow state.

In order to prevent the surface oxidation of the copper powder particles of the tens of nm grade to prevent the micronization, in order to reduce the specific surface area, it has been attempted to produce a submicron-sized particle larger than several tens of nm by the plasma method, but using high-frequency electricity. In the method for producing a slurry, the length of the generated plasma flame has a limit, and it is very difficult to manufacture a submicron-sized particle system controlled to be 100 nm or more.

Further, in the wet reduction method, although submicron-sized particles can be produced, they are produced by a redox reaction in an aqueous solution, and the effect of reducing the surface oxidation of the particles due to the influence of surface adsorption of water or the like is limited. Reduced to 10 ^-1 Ω. The level of cm≦ is still difficult.

From such a viewpoint, it is preferable to use a DC plasma device to atomize the copper powder particles.

As a DC plasma apparatus, for example, as shown in FIG. 1, a plasma apparatus 1 including a powder supply device 2, a reaction chamber 3, a DC plasma torch 4, a recovery tank 5, a powder supply nozzle 6, and a gas supply are provided. Device 7 And a pressure adjusting device 8.

In this apparatus, the raw material powder is introduced into the inside of the DC plasma torch 4 from the powder supply device 2 through the powder supply nozzle 6. The plasma torch 4 supplies a mixed gas of argon and nitrogen from the gas supply device 7 to generate a plasma flame.

Further, in the plasma flame generated by the DC plasma torch 4, the raw material powder is gasified and released into the reaction chamber 3, and then cooled to become fine powder and stored in the recovery tank 5.

The inside of the reaction chamber 3 is controlled to maintain a negative pressure with respect to the powder supply nozzle 6 by the pressure adjusting device 8, and has a structure in which a plasma flame is stably generated.

However, an example of such a DC plasma device is not limited to such a device.

The raw material copper powder system is not particularly limited. However, the particle size (D50) of the raw material copper powder is preferably from 3.0 μm to 30 μm from the viewpoint of plasma sprayability, and more preferably 5.0 μm or more or 15 μm or less.

Further, the shape of the raw material copper powder is not particularly limited as long as it is dendritic, rod-shaped, fragmented, cubic, or spherical or substantially spherical. However, from the viewpoint of stabilizing the supply efficiency of the plasma torch, it is preferably a spherical shape or a substantially spherical shape.

When the copper raw material powder is heated and sprayed by using a DC plasma device, a mixed gas of argon and nitrogen is used as the plasma gas, and the plasma flame is laminar and adjusted to be wider and longer. When adjusted in this way, the raw material copper powder that is input is vaporized instantaneously in the plasma flame and can supply sufficient energy in the plasma flame, so that the core can be formed toward the plasma tail flame portion and Agglomeration and condensation are formed to form microparticles, especially submicron-sized microparticles.

As described above, the plasma flame is in a laminar flow state and it is preferable to adjust the plasma output power and gas flow rate in such a manner as to be wide and long. From this point of view, the plasma output power of the direct current thermal plasma device is preferably 2 kW to 30 kW, and more preferably 4 kW or more or 15 kW or less. Further, from the above viewpoints, the gas flow rate of the plasma gas is preferably from 0.1 L/min to 20 L/min, and more preferably from 0.5 L/min to 18 L/min.

Moreover, in order to stably maintain the plasma flame in a laminar flow state, the above-mentioned plasma output power and gas flow rate range are maintained, and the sum of the Ar gas flow rate (B) and the N ₂ gas flow rate (C) is applied to the plasma. The ratio of the output power (A) is preferably 0.50 or more and 2.00 or less, which is calculated by the calculation formula (B+C)/A (unit: L/(min. kW)). In order to obtain a flow rate necessary for gasification of the raw material powder, the (B+C)/A value is preferably set to 0.50 or more, and in order to maintain the laminar flow of the plasma flame and to be stable, it is preferably set to 2.00 or less. .

From this point of view, (B+C)/A is particularly preferably adjusted so as to be 0.70 or more or 1.70 or less, and more preferably adjusted to 0.75 or more or 1.50 or less.

As the plasma gas for the operating gas generated by the hot plasma, as described above, a mixed gas of argon and nitrogen is preferably used.

Here, when a gas in which an argon gas and a nitrogen gas are mixed is used, a nitrogen (2 atomic molecule) gas can impart a larger vibration energy (thermal energy) to the copper powder particles, and the aggregated state can be made uniform. Get the particle size distribution Sharper nano particles.

However, when the content of nitrogen is too large, the plasma flame is degraded and a powder having a sharp particle size distribution cannot be obtained.

From this point of view, the ratio of argon to nitrogen in the plasma gas is preferably from 99:1 to 10:90 in flow ratio, with 95:5 to 60:40, of which 95:5 to 80:20. For better. Further, from the viewpoint of making the particle size distribution sharp, in other words, from the viewpoint of making (D90-D10)/D50 smaller, the ratio of argon to nitrogen is in a flow ratio of 99:1 to 50:50, of which 95 The mode of 5 to 50:50 is preferably adjusted within a ratio of the flow rate of argon to more than nitrogen.

The copper powder obtained as described above can also be used as it is, but it is more preferable to carry out classification to remove coarse aggregated particles and foreign matter which are contaminated. At this time, the classification is carried out by using an appropriate classifying device to be the center of the particle size as the target, and separating the coarse powder and the fine powder.

(shape processing)

The copper powder can also be used directly, but the copper powder can also be used after being processed into a shape.

For example, a spherical particle powder (80% or more of a powder composed of spherical particles) can be mechanically processed into a non-spherical particle powder such as a chip, a scaly or a flat plate (: 80 % or more of powder composed of non-spherical particles).

More specifically, it can be mechanically flattened (pressed or stretched) by using a bead mill, a ball mill, a vertical ball mill, a vibration mill, or the like, and processed into a chip-like particle powder by shape (: 80% or more a powder composed of fragmented particles). At this time, in order to prevent aggregation and bonding between particles, At the same time, it is preferred to carry out processing in a state in which the respective particles are independent, and to add an auxiliary agent such as a fatty acid such as stearic acid or a surfactant. Further, the copper powder processed by such a shape may be used, or the unshaped raw powder may be mixed and used.

<Use>

The copper powder is used alone or in combination with other copper powder such as a chip-like powder, and is also suitable as a conductive filler for use in any of, for example, a resin-curable conductive paste and a calcined conductive paste.

Further, when a coating film is produced using the paste of the present copper powder, a coating film having high conductivity and high smoothness can be produced. This is considered to be due to the fact that since the copper powder has a very high crystallinity, it has few crystal grain boundaries which are a hindrance factor for conduction and an inducer of oxidative coagulation.

Therefore, the present copper powder may be used alone or in combination with other copper powder such as a pulverized powder, or may be formulated with an organic binder composed of a thermosetting resin such as an epoxy resin to prepare a resin-curable conductive material. paste. Further, the copper powder may be used alone or in combination with other copper powder such as flaky powder, or may be formulated in an organic vehicle to prepare a calcined conductive paste.

A conductive paste containing a conductive filler in a mixed powder of the present copper powder or the present copper powder can be suitably used as, for example, a conductor circuit for screen printing, an external electrode for a laminated ceramic capacitor, or the like as various electrical contact members. Conductive paste used.

Also. The copper powder or the mixed powder containing the copper powder can be used as an electrode of a chip element such as an internal electrode, an inductor, or a resistor of a multilayer ceramic capacitor, a single-plate capacitor electrode, a tantalum capacitor electrode, or the like. Conductor circuit of resin multilayer substrate, conductor circuit of ceramic (LTCC) multilayer substrate, conductor circuit of flexible printed circuit board (FPC), antenna switch module circuit, PA module circuit, active filter, etc. Group circuit, PDP front panel and back panel, electromagnetic shielding film for PDP color filter, crystal solar cell surface electrode and back extraction electrode, conductive adhesive, EMI shielding, RF-ID, and PC keyboard A conductive material such as a switch, an anisotropic conductive film (ACF/ACP), a joint member of an electronic component and a semiconductor, and a paste for circuit repair.

<Description of the statement>

In the present specification, when "X to Y" (X, Y is an arbitrary number), it is "X or more and Y or less" unless otherwise specified in advance, and "Better than X" or "better than X" or "It is better to be less than Y".

In addition, when expressing "X or more" (X-type arbitrary number) or "Y below" (Y-type arbitrary number), it is intended to include "being greater than X" or "being less than Y".

[Examples]

Hereinafter, the present invention will be described in further detail based on the following examples and comparative examples.

<Example 1>

In this embodiment, a DC plasma micropowder manufacturing apparatus was used to produce copper powder in accordance with the following.

Copper powder (particle diameter: 10 μm, spherical particles) was introduced as a raw material powder from the raw material powder supply port, and an Ar flow rate of 13.0 L/min and an N ₂ flow rate of 0.7 L/min were used as a slurry at a raw material supply amount of 10 g/min. The gas is supplied to the inside of the plasma flame (in other words, the plasma flame). At this time, the ratio of the Ar flow rate (B) to the N ₂ flow rate (C) is 95:5. Further, the plasma output power was 10.0 kW, and the plasma output power (A), the Ar flow rate (B), and the N ₂ flow rate were adjusted to become (B + C) / A = 1.37 (L / (min. kW)).

The copper powder obtained in this manner is stored in a recovery tank, and the copper powder (sample) is recovered after the production batch is slowly opened to the atmosphere.

In the above manufacturing method, regarding the generated Plasma flame (in other words, the plasma flame), the plasma flame is photographed from the side where the flame width is the widest, and the flame length is determined by binarization. Ratio (flame aspect ratio) (the same applies to the examples and comparative examples described later). As a result, the generated plasma flame had a flame aspect ratio of 4 and was confirmed to be laminar.

<Example 2>

In Example 1, except that the plasma power output (A), Ar flow (B) and the N ₂ flow (C) are each adjusted to become as shown in Table 1 the Ar flow rate (B) and the N ₂ flow rate (C) of Copper powder (sample) was obtained in the same manner as in Example 1 except that the gas ratio was changed to 90:10. At this time, the generated plasma flame has a flame aspect ratio of 5 and is a laminar flow.

<Example 3>

In Example 1, except that the plasma power output (A), Ar flow (B) and the N ₂ flow (C) are each adjusted to become as shown in Table 1 the Ar flow rate (B) and the N ₂ flow rate (C) of Copper powder (sample) was obtained in the same manner as in Example 1 except that the gas ratio was changed to 85:15. At this time, the generated plasma flame has a flame aspect ratio of 7 and is a laminar flow.

<Example 4>

In Example 1, except that the plasma power output (A), Ar flow (B) and the N ₂ flow (C) are each adjusted to become as shown in Table 1 the Ar flow rate (B) and the N ₂ flow rate (C) of Copper powder (sample) was obtained in the same manner as in Example 1 except that the gas ratio was changed to 80:20. At this time, the generated plasma flame has a flame aspect ratio of 8 and is a laminar flow.

<Example 5>

In Example 1, except that the plasma power output (A), Ar flow (B) and the N ₂ flow (C) are each adjusted to become as shown in Table 1 the Ar flow rate (B) and the N ₂ flow rate (C) of Copper powder (sample) was obtained in the same manner as in Example 1 except that the gas ratio was changed to 70:30. At this time, the generated plasma flame has a flame aspect ratio of 7 and is a laminar flow.

<Example 6>

In Example 1, except that the plasma power output (A), Ar flow (B) and the N ₂ flow (C) are each adjusted to become as shown in Table 1 the Ar flow rate (B) and the N ₂ flow rate (C) of Copper powder (sample) was obtained in the same manner as in Example 1 except that the gas ratio was changed to 60:40. At this time, the generated plasma flame has a flame aspect ratio of 6 and is a laminar flow.

<Example 7>

In Example 1, except that the plasma power output (A), Ar flow (B) and the N ₂ flow (C) are each adjusted to become as shown in Table 1 the Ar flow rate (B) and the N ₂ flow rate (C) of Copper powder (sample) was obtained in the same manner as in Example 1 except that the gas ratio was changed to 40:60. At this time, the generated plasma flame has a flame aspect ratio of 4 and is a laminar flow.

<Example 8>

In Example 1, except that the plasma power output (A), Ar flow (B) and the N ₂ flow (C) are each adjusted to become as shown in Table 1 the Ar flow rate (B) and the N ₂ flow rate (C) of Copper powder (sample) was obtained in the same manner as in Example 1 except that the gas ratio was changed to 10:90. At this time, the generated plasma flame has a flame aspect ratio of 3 and is a laminar flow.

<Comparative Example 1>

In Example 1, except that the plasma power output (A), Ar flow (B) and the N ₂ flow (C) are each adjusted to become as shown in Table 1 the Ar flow rate (B) and the N ₂ flow rate (C) of Copper powder (sample) was obtained in the same manner as in Example 1 except that the gas ratio was changed to 100:0.

At this time, the generated plasma flame is in a state of turbulence and the flame is oscillated to the left and right.

<Comparative Example 2>

Copper powder (sample) was obtained by the wet reduction method as follows.

The copper sulfate pentahydrate was added to 6.5 L of pure water at 65° C. so as to have a copper concentration of 3.7 mol/L, and after stirring, 0.61 mmol of sodium pyrophosphate was added to 1 mol of copper, and stirring was continued in this state. Minutes to obtain an aqueous solution containing copper.

In the state after the aqueous solution was stirred, about 0.88 mol of ammonia water per 1 mol of copper and 0.87 mol of sodium hydroxide per mol of copper were simultaneously added to the aqueous solution to form copper oxide. Then, stirring was continued for 30 minutes.

Next, a first reduction reaction is carried out by adding 1.17 mol of ruthenium to 1 mol of copper and 0.40 mol of ammonia per 1 mol of copper to make the copper oxide further Originally made of cuprous oxide. Then, stirring was continued for 30 minutes.

Next, a ruthenium of 0.39 mol per 1 mol of copper was added to the liquid to carry out a second reduction reaction, and the cuprous oxide was reduced to copper. Stirring was continued for 1 hour to complete the reaction. After completion of the reaction, the obtained slurry was filtered using a Nuche funnel, and then washed with pure water, dried at 70 ° C for 5 hours under vacuum, and then slowly returned to the atmosphere. The copper particles of the purpose are obtained by the environment.

<Evaluation of copper powder (sample)>

The copper powder (sample) obtained in the examples and the comparative examples was evaluated for various characteristics by the method described below.

(1) Observation of particle shape

The copper powder (sample) obtained in the examples/comparative examples was observed in any of 10 fields using a scanning electron microscope (2,000 times), and the shape of each of the 500 particles was observed, and it was observed that 80% of the particles were observed. When the shape is, its shape is shown in Table 2.

(2) Average particle size of primary particles Dsem

The copper powder (sample) obtained in the examples/comparative examples was imaged by a scanning electron microscope (magnification: 10,000 times or 30,000 times), and the primary particle diameter of any 200 particles in the visual field was measured using an image analysis software. The ball was converted and measured, and the average value of the obtained 200 primary particle diameters converted into spheres was defined as "average particle diameter Dsem (μm) of primary particles".

(3) Particle size distribution

0.2 g of copper powder (sample) was added to 100 ml of pure water and dispersed by ultrasonic waves (3 minutes), and then subjected to laser diffraction/scattering particle size distribution measurement. The device (Microtrac (trade name) FRA (model)) manufactured by Nikkiso Co., Ltd.) was used to measure volume cumulative particle diameters D10, D50, and D90.

(4) crystallite diameter

The diffraction peak of the (111) plane obtained by X-ray diffraction of copper powder was analyzed using RINT-TTRIII manufactured by Rigaku, and the crystallite diameter (nm) was calculated using the Scherrer method.

(5) BET specific surface area (SSA)

Using the MONOSORB (trade name) manufactured by YUASA-IONICS Co., Ltd. and the "3.5) one-point method of the 6.2 flow method according to JIS R1626-1996 (method for measuring the specific surface area of the gas adsorption BET method using fine ceramic powder), The BET specific surface area (SSA) was measured. At this time, a mixed gas of a carrier gas and a nitrogen of an adsorbate gas is used.

(6) Oxygen/nitrogen amount

The oxygen amount and the amount of nitrogen of the copper powder (sample) were analyzed using an oxygen/nitrogen analyzer ("EMGA-520 (model)" manufactured by Horiba, Ltd.).

(7) Powder pressure resistor

The powder resistance value was measured using a powder resistance measurement system (PD-41 manufactured by Mitsubishi Chemical Corporation, Inc.) and a resistivity meter (MCP-T600 manufactured by Mitsubishi Chemical Corporation, Inc.).

5 g of copper powder (sample) was placed in the probe cartridge and the probe unit was mounted on the PD-41. The resistance value at the time of applying a load of 18 kN by the hydraulic jack was measured using a resistivity meter. The volume resistivity (compressor resistance) was calculated from the measured resistance value and the sample thickness.

(8) Evaluation of conductivity of coating film

= conductivity evaluation paste adjustment =

20 g of copper powder, 0.3 g of ethyl cellulose polymer (Ethocel manufactured by Nisshin Kasei Co., Ltd.), and 3.7 g of terpineol (Tepineol) were weighed and pre-kneaded using a doctor blade, and then a spinning/revolving vacuum mixer (THINKY) was used. The company-made ARE-500) was subjected to two cycles of a stirring mode (1000 rpm × 1 minute) and a defoaming mode (2000 rpm × 30 seconds) to be one cycle, and became a paste. The paste was further treated five times in total using a three-roll mill, and dispersed and mixed to prepare a paste A.

= Formation of coating film for conductivity evaluation =

The paste A prepared in this manner was applied onto a glass substrate using an applicator and a gap of 35 μm. Subsequently, it was dried by heating at 150 ° C for 10 minutes in a nitrogen oven, and further calcined at 300 ° C for 1 hour in a nitrogen oven to prepare a coating film.

= Determination of volume resistivity =

The volume resistivity (Ω.cm) of the coating film was measured by a four-probe method using a resistivity meter (Loresta GP: MCP-T610 manufactured by Mitsubishi Chemical Corporation) and a probe (QPP manufactured by Hioki Electric Co., Ltd.). At this time, the film thickness was a value measured by a film thickness meter.

Based on the value of the volume resistivity (Ω.cm), the following determination was made.

AA: Less than 1×10 ^-5 (best)

A: 1 × 10 ^-5 or more and less than 1 × 10 ^-4 (good)

B: 1 × 10 ^-4 or more (poor)

(9) Smoothness evaluation of coating film

= smoothness evaluation paste adjustment =

The same method as the above-mentioned paste A was used except that 20 g of copper powder, 1.9 g of ethyl cellulose polymer (Ethocel manufactured by Nisshin Kasei Co., Ltd.), and 11.7 g of terpineol were weighed. (The paste obtained by this is referred to as paste B).

= Formation of smoothness evaluation coating film =

The paste B described above was applied onto a glass substrate using an applicator and a gap of 35 μm. Subsequently, the film was dried by heating at 150 ° C for 10 minutes in a nitrogen oven to obtain a coating film for smoothness evaluation.

= Determination of surface roughness =

The center line average roughness Ra (μm) of the coating film described above was measured in accordance with JIS B 0601-1982 using a surface roughness meter (SURFCOM 480B-12 manufactured by Tokyo Seimitsu Co., Ltd.).

Moreover, the following determination is performed from the value of the center line average roughness Ra (μm).

AA: Less than 0.1 (best)

A: 0.1 or more is less than 0.2 (good)

B: 0.2 or more (poor)

= Comprehensive evaluation =

The electrical conductivity and smoothness of the above-mentioned coating film were comprehensively determined based on the following criteria.

AA: Conductivity and smoothness are both AA (best)

A: Conductivity and smoothness are all above A (good)

B: Conductivity or smoothness is B (poor)

From the results of the above examples and the results of experiments conducted by the inventors of the present invention, it is found that the ratio of the diameter of the copper powder-based crystallites to the D50 (crystallite diameter/D50) of the examples is 0.15 to 0.60 (μm/μm). The crystallite diameter is large, even if the D50 is from 0.20 μm to 0.70 μm of the particulate copper powder, Since the crystallite diameter is also large, the conductive paste of the copper powder is used, and the coating film has excellent electrical conductivity and smoothness.

1‧‧‧ Plasma device

2‧‧‧Powder supply device

3‧‧‧Reaction room

4‧‧‧DC Plasma Torch

5‧‧‧Recycling tank

6‧‧‧Powder supply nozzle

7‧‧‧ gas supply device

8‧‧‧ Pressure adjustment device

Claims (6)

A copper powder characterized in that the volume cumulative particle diameter D50 measured by a laser diffraction scattering type particle size distribution measuring apparatus is 0.20 μm to 0.70 μm, and the ratio of the crystallite diameter to the D50 (crystallite diameter/ D50) is 0.15 to 0.60 (μm/μm). The copper powder according to claim 1, wherein a ratio of oxygen amount (O amount) to surface area is 0.10 to 0.40 (wt%.g/m ² ). The copper powder according to claim 1 or 2, wherein the volume cumulative particle diameter D90 measured by the laser diffraction scattering type particle size distribution measuring apparatus is from 0.35 μm to 12.0 μm. The copper powder according to any one of claims 1 to 3, wherein the volume cumulative particle diameter D10 measured by the laser diffraction scattering type particle size distribution measuring apparatus is from 0.08 μm to 0.30 μm. The copper powder according to any one of claims 1 to 4, wherein 50% or more of the copper powder particles constituting the copper powder are spherical or substantially spherical. The copper powder according to any one of claims 1 to 5, wherein the formula (D90-D10)/D50 (unit: μm/μm) expressed by the aforementioned D90, D10 and D50 is 1.0 to 7.0.