JPH0234708A - Manufacture of copper fine powder - Google Patents

Abstract

PURPOSE:To manufacture spherical shaped copper fine powder having monodisperse and narrow particle size distribution in short time at low cost by reducing copper oxide powder with hydrazine after coating the surface of the copper oxide powder with silane coupling agent. CONSTITUTION:The surface of the copper oxide powder having the prescribed particle size is coated with the silane coupling agent. This coating method is desirable to execute dy charging the copper oxide powder and the silane coupling agent, or water solution or alcohol solution of the silane coupling agent into a mixer or a pulverizing machine, and mixing or pulverizing. Successively, this coated copper oxide powder is reduced with the hydrazine. Then, while dispersing and stirring the above silane coupling agent-coated copper oxide powder in the water, the hydrazine or the hydrazine water solution is added to this and if necessary, this mixed suspending solution is desirable to heat at about 60 deg.C. By this method, the spherical copper fine powder having high purity is obtd. in short time at low cost.

Description

[Detailed Description of the Invention] [Industrial Application] The present invention is for forming thick film conductors for electronic circuits! Ii
The present invention relates to a method for producing fine spherical copper powder in which particles are monodispersed, which is particularly useful as an i-coating.

[Conventional technology]

vA paints have recently gained attention as an alternative to the silver or palladium paints currently used to form thick film conductors in electronic circuits. This copper paint usually has 0.2
Fine copper powder of μm to 10 μm is used, but in order to obtain a dense copper conductor film when the paint is baked, spherical fine copper powder with monodisperse particles, no agglomeration, and few impurities is desired. There is. In addition, in order to obtain a dense copper conductor film, two to three kinds of narrow powders with a narrow particle size distribution are mixed and used in order to obtain the densest optical fiber, and the copper powder used for this is It is required to be a monodispersed powder that is spherical and has a uniform particle size.

Conventionally, various methods for producing fine copper powder have been proposed, but the method for producing copper powder with a particle size of 0.2 μm to 10 μm is: ■ Mixing a copper-containing solution containing copper carbonate with hydrazine or a hydrazine compound. This method is then heated to reduce and precipitate copper powder. (Unexamined Japanese Patent Publication No. 57-155302
No.) ■A method of reducing copper oxide with hydrazine and/or a hydrazine compound in an aqueous medium containing a protective colloid. (Japanese Patent Publication No. 61-55562) ■In the method of producing copper fine particles by reducing an aqueous copper sulfate solution using hydrazine as a reducing agent, monodispersed copper fine particles are obtained by adding a surfactant to the reaction solution. Method. (JP-A-62-27508, JP-A-62-27508)
No. 40302, JP-A-62-77407, JP-A-62
-77408) etc. However, these conventional methods (a)
It is not possible to obtain a copper powder that satisfies all of the following conditions: uniform particle size, (b) monodispersion, (C) low impurities, and (d) spherical shape.

That is, in the method (2) of reducing copper carbonate with hydrazine, the copper powder aggregates during precipitation, resulting in irregular shapes. Further, in the method (2) in which copper oxide is reduced in an aqueous medium containing a protective colloid, the agglomeration of copper powder is prevented to some extent by the protective colloid, but it is not satisfactory. In experiments conducted by the present inventors, when a powder with an average particle size of 1.5 μm is produced by this method, a powder having a particle size in the range of 0.7 μT11 to 8 μm is obtained. A further problem with this method is that if a protective colloid, ie, an organic compound such as gum arabic, remains in the copper powder, it will worsen the firing atmosphere during firing of the thick film conductor, which is undesirable for forming a thick film.

In addition, in the method (2) in which an aqueous copper sulfate solution is reduced with hydrazine in the presence of a surfactant, copper is precipitated from a water-soluble copper compound, so the particle size during precipitation varies, for example, the average particle size is 2.5 μm. It contains powder with a particle size of 0.5 μm to 8 μm.

[Problems to be solved by the present invention]

The present invention is a production method in which a copper compound is reduced in an aqueous solution from the viewpoint of production cost advantages, and it is possible to obtain monodispersed spherical fine copper powder even in a short time without affecting the particle shape depending on the reaction time. As a result of conducting research on a method for producing fine copper powder that has a narrow particle size distribution and can change the particle size to some extent, it was found that the solution could be solved by surface-treating copper oxide with a silane coupling agent in advance and reducing it with an aqueous solution containing hydrazine. The present invention was completed by discovering that

[Means for solving problems]

That is, the present invention is a method for producing fine copper powder, which comprises coating the surface of copper oxide powder with a silane coupling agent and then reducing the copper oxide powder with hydrazine.

[Effect]

The starting copper compound of the present invention must be copper oxide, and as the copper oxide, either cuprous oxide or cupric oxide can be used, and both give almost the same results.

If a copper salt other than copper oxide, such as copper sulfate, copper nitrate, or copper acetate, is used as a starting material, a large amount of non-spherical fine copper powder will precipitate, which is not good. In addition, if copper hydroxide or copper bromide are used as starting materials, they will be more spherical than those using copper salts, but they will contain more irregular powder than copper oxide, and the particle size distribution will be broader, which is not good. .

In order to produce fine spherical copper powder with a narrow particle size distribution, it is necessary to use copper oxide as a starting material, but when copper oxide is used, the particle size (also called average particle size) of the fine copper powder can be changed to a certain degree. be able to. In other words, there is a certain correlation between the particle size of the copper oxide powder and the particle size of the precipitated copper fine powder; if the copper oxide powder particle size is large, the copper fine powder will also be large, and if the copper oxide powder particle size is small, the copper fine powder will also be small. Become.

Furthermore, copper oxide has a higher copper content than other copper compounds, and is also characterized by being inexpensive as a raw material for depositing copper powder.

In the present invention, the surface of the copper oxide powder is coated with a silane coupling agent.
Even if the particle size of copper oxide powder is increased, no coarse agglomerates are formed, and even if small copper oxide powder is used, it does not form into a fine colloid, and a fine copper powder with uniform particle size can be obtained.

The silane coupling agent in the present invention is an organosilicon compound whose chemical structural formula is represented by the general formula Y RS i X 3. Here, Y is an organic functional group such as a vinyl group or an amino group. R is an alkyl group, and X is a hydrolyzable group such as a methoxy group or an ethoxy group. The silane coupling agent used for manufacturing fine copper powder that forms thick film conductors of electronic circuits is preferably one that does not contain S or Ct in its chemical structure and does not react violently with water.

Hydrolyzable groups with chloro groups react violently with water and are not good.

As a silane camping agent, Vinyl-tris (β-a+ethoxyetho
xy) silane.

7-Glycidoxypropyltrimetho
xysilane.

7-Aminopropyltriethoxysil
ane.

N-β-(AI++1noeLhyl)-7-amin
opropyltrimethoxysilane.

7-Ureidopropyltriethoxysi
lane, etc. are suitable.

The amount of silane coupling agent is 0.0% by weight relative to copper oxide.
It is effective from 51wtχ and up to 20wtχ is an appropriate amount, and adding more than this has little effect and is not economical.

To coat copper oxide with a silane camping agent, the silane camping agent may be directly added to the copper oxide, or an aqueous solution or an alcoholic solution of the silane camping agent may be added to the copper oxide, and the mixture may be stirred and mixed or crushed.

When a silane coupling agent is used in an aqueous or alcohol solution, the surface of the copper oxide powder can be coated quickly (uniformly).However, if the concentration of the silane coupling agent in the water or alcohol solution is low, the silane coupling agent Therefore, when preparing a water or alcohol solution, it is preferable to add 20wL% or more of the silane coupling agent.

As a mixer for stirring and mixing, a normal mixer, kneader, etc. can be used. When carrying out the process while pulverizing, it is possible to efficiently perform the pulverizing and coating treatment using a pulverizer such as a ball mill, attritor, or vibrating mill that uses balls as the pulverizing medium.

In the present invention, forming a coating of a silane coupling agent on the surface of copper oxide while grinding is important when producing fine copper powder with a small particle size.

When the copper oxide powder becomes small, it becomes difficult to uniformly form a coating with a silane coupling agent, and the effects of the present invention may not be sufficiently obtained. In particular, when trying to obtain small copper oxide powder using small copper oxide powder, add a silane coupling agent to large copper oxide powder and grind it to uniformly coat it into small copper oxide powder. It is a better method to easily obtain uniform spherical copper fine powder with uniform particle size.

As the reducing agent used in the present invention, hydrazine and hydrazine hydrate are suitable, and hydrazine compounds such as hydrazine hydrochloride and hydrazine sulfate can also be used, but these are not preferred because they cause problems in cleaning.

Reducing agents other than hydrazine include formaldehyde, glucose, hypophosphorous acid, and sodium borohydride, but they have weak reducing power and cannot reduce copper oxide to metallic copper, and even if reduced and precipitated, the particle size distribution is wide. Only irregularly shaped copper powder can be obtained.

The amount of hydrazine as a reducing agent is related to the amount of the aqueous solution, but is basically determined by the amount of copper oxide. A reduction reaction is observed when the amount of hydrazine relative to copper oxide is 10-tχ by weight, but the reaction proceeds more quickly and is completed in a shorter time when 50 wt % or more is added.

Note that the reaction progresses faster as the amount of hydrazine is increased, but adding more than 200wt% results in the same reaction, which is not economical.The amount of aqueous solution in which the copper oxide coated with the silane coupling agent is dispersed and suspended is determined by the amount of copper oxide that is well stirred. The amount may be as long as it can be used, preferably about 50 times the volume of copper oxide, but there is no particular limitation if stirring is not performed.

Although the reduction reaction can be observed at room temperature, the reaction rate is slow and it takes a long time to complete the reaction, so it is better to heat it to 60'C or higher.

In order to obtain fine copper powder in a short time, it is best to increase the amount of hydrazine and heat it to 60°C or higher, so that the fine copper powder obtained will not become irregular in shape due to dirt.

The reaction vessel used to carry out the present invention is preferably equipped with a stirring device, and the reaction vessel is preferably made of glass to prevent elution of impurities, but may be made of stainless steel or a vessel coated with Teflon or the like.

To explain the reduction process of fine copper powder in the method of the present invention, copper oxide coated with a silane coupling agent is dispersed and suspended in an aqueous solution, hydrazine is added while stirring, and the mixture is gradually heated to the reduction reaction temperature. The black or reddish-brown suspension gradually turns red and then copper. If this is left to stand, fine copper powder will settle at the bottom, and the top will turn into a colorless and transparent liquid. The precipitated fine copper powder is taken out, washed with an organic solvent such as alcohol or acetone, and dried by a conventional method to obtain a monodispersed fine spherical copper powder with a uniform particle size of 10 μm or less.

Although it is not fully understood that monodispersed spherical copper fine powder can be obtained by using copper oxide coated with a silane coupling agent even if the reaction rate is increased, it is thought to be as follows.

The silane coupling agent coated on the surface of the copper oxide powder undergoes hydrolysis and becomes silanol, forming a siloxane bond on the surface of the copper oxide.

Until now, it has been said that in order to obtain monodispersed spherical fine copper powder, it is sufficient to lower the copper ion concentration and conduct the reaction slowly. In other words, when the copper ion concentration is increased or the reaction rate is increased, many copper nuclei are generated at once, and the nuclei agglomerate with each other during the growth stage, resulting in irregularly shaped copper fine powder.

It is thought that the siloxane bonds formed on the copper oxide surface prevent the aqueous solution from approaching to some extent and control the copper ion concentration in the aqueous solution so that it does not exceed a certain level even in the presence of a reducing agent.

In other words, it is thought that the concentration of copper ions in the aqueous solution is controlled from the beginning of the reaction to near the end of the reaction to prevent too many nuclei from forming and aggregating at the same time.

The smaller the nucleus grows, the faster it grows, and the larger the nucleus, the slower it grows, so even if the nucleus continues to be generated from the beginning of the reaction to near the end of the reaction, the diameter of the fine copper powder obtained is very uniform. It becomes complete.

It is thought that the silane coupling agent does not prevent the reduced and precipitated fine copper particles from sticking together, but has the effect of controlling the copper ion concentration in the reaction solution to obtain monodispersed spherical copper fine powder.

〔Example〕

Examples of the present invention are shown below.

Example (1) A silane coupling agent Vinyl-tris (β-methoxye
Add 5g of Lhoxy) stlane and mix with a mixer for 10
The mixture was stirred and mixed for a minute, and then the entire amount was dispersed and suspended in 500 cc of an aqueous solution. Then, 50 g of hydrazine l hydrate was added while stirring, and the mixture was gradually heated to 70° C. after 15 minutes. When the suspension was maintained at 70° C. for 15 minutes, the reaction was completed and fine copper powder was precipitated.

Filter it out with an aspirator, wash it with acetone, and then
Air dried at °C.

39 g of fine copper powder was obtained, and when the particle size and shape of the powder was observed under an electron microscope, it was found to be a monodisperse spherical powder with a uniform size of 1 μm to 1.5 μm and no agglomeration. As a result of measuring the amount of oxygen as an impurity, it was very low at 0.12χ, and the amount of Si was also 0.0
The amount was extremely small at 032.

Example (2) Using the same cupric oxide as in Example (+), only the silane coupling agent for surface treatment of cupric oxide was 7-Glycid.
oxypropyltrimethoxysilane
Copper fine powder was obtained in the same manner as in Example (1) except that .

39g of fine copper powder was obtained, and when the particle size and shape of the powder was observed using an electron microscope, it was a monodisperse spherical powder with a uniform size of 1μ to 1.5μm without agglomeration, and the oxygen content was also extremely high at 0.13χ. There were very few.

Example (3) Using the same cupric oxide as in Example (1), only silane coupling agent for surface treatment of cupric oxide was used.
Fine copper powder was obtained in the same manner as in Example (1) except that ropyltriethoxysilane was used.

A fine copper powder of 39 was obtained, and when the particle size and shape of the powder was observed using an electron microscope, it was found to be 1. It is a monodisperse spherical powder with a uniform size of cza+-1.5μm and no agglomeration, and the oxygen content is 0614χ
There were very few.

Example (4) Using the same cupric oxide as in Example (1), only the silane coupling agent for surface treatment of the cupric oxide was N-β (Amin
oethyl)-y-aminopropyltrim
Example (1) except that it was changed to ethoyxsilane
Copper fine powder was obtained in the same manner as above.

39g of fine copper powder was obtained, and when the particle size and shape of the powder was observed using an electron microscope, it was a monodisperse spherical powder with a uniform size of 1 μm to 1.5 μm without agglomeration, and the amount of oxygen was very high at 0.132. It was small.

Example (5) Using the same cupric oxide as in Example (]), only a silane coupling agent for surface treatment of cupric oxide γ-Ureid
Copper fine powder was obtained in the same manner as in Example (1) except that opropyltriethoxysilane was used.

39 g of fine copper powder was obtained, and when the particle size and shape of the powder was observed under an electron microscope, it was a monodisperse spherical powder with uniform 1μIm to 1.5μ steel without agglomeration, and the oxygen content was 0. It was very small at 14χ.

Example (6) Cupric oxide 10 with the same average particle size of 10 μI as Example (1)
Using 0g of silane coupling agent γ-m1nopr
0.5 g of opyltriethoxysilane was added and the mixture was pulverized for 30 minutes with an attritor using a 5Iφ stainless steel pole as a pulverizing medium.The average particle size of the cupric oxide after pulverization was 5 μm.

Disperse and suspend 50 g of cupric oxide with an average particle size of 5 μm, which has been surface-treated while being crushed in this way, in 500 cc of aqueous solution, then add 50 g of vitrazine l permanent while stirring, and after 15 minutes the temperature reaches 70°C. It was gradually warmed up.

The reaction was completed when the suspension was held at 70°C for 515 minutes.
Fine copper powder was precipitated. After filtration with an aspirator, it was washed with acetone and then air-dried at 20''C.

39 g of fine copper powder was obtained, and when the particle size and shape of the powder was observed under an electron microscope, it was a monodisperse spherical powder with a uniform size of 0.5 μm = 0.8 μm and no agglomeration. As a result of measuring the amount of oxygen as an impurity, it was found to be very small at 0.19χ.

Example (7) Cupric oxide 10 with the same average particle size of 10 μm as Example (1)
0 g of silane coupling agent 7-Am1no
5 g of propyltriethoxysilane was added and crushed for 180 minutes with an attritor using a 5 mmφ stainless steel pole as a crushing medium. The average particle size of cupric oxide after pulverization was 0.5 μm.

The average particle size Q of the surface treated while being crushed in this way is 5μ.
Disperse and suspend 50 g of cupric oxide (m) in 500 cc of aqueous solution, and then add 50 g of bitrazine monohydrate while stirring.
After 20 minutes, the mixture was gradually heated to 60°C. When the suspension was maintained at 60°C for 920 minutes, the reaction was completed and fine copper powder was precipitated. After filtration with an aspirator, it was washed with acetone and then air-dried at 20°C.

37 g of fine copper powder was obtained, and when the particle size and shape of the powder was observed under an electron microscope, it was a monodisperse spherical powder with a uniform size of 0.3 μm to 0.5 μm and no agglomeration. As a result of measuring the amount of oxygen as an impurity, it was 0.192, which was very small.

Example (8) Silane coupling agent Vinyl-tris (β-#e tho
Add 5g of Vitrazine Lhoxy) silane, stir and mix with a mixer for 10 minutes, then disperse and suspend in a total amount of 500cc of aqueous solution, then add 50g of Vitrazine Lhoxylate with stirring, and heat to 60°C after 15 minutes. Warm up gradually.

The reaction was completed when the suspension was held at 60°C for 115 minutes.
Fine copper powder was precipitated. After filtering with an aspirator, it was washed with acetone and then air-dried at 20°C.

44g of fine copper powder was obtained, and electron';! When the particle size and shape of the powder was observed using an R@mirror, it was a monodisperse spherical powder with a uniform size of 2 μm to 2.5 μm and no agglomeration. As a result of measuring the amount of oxygen as an impurity, it was found to be very small at 0.11χ.

Example (9) Silane camping agent 7-Am1nopropyl trieth was added to 50 g of cuprous oxide having an average particle size of 10 μl.
Add 5g of oxysilane, stir and mix with a mixer for 10 minutes, then disperse and suspend in 1i500cc of aqueous solution, then add 2g of hydrazine l hydrate with stirring.
5g was added, and the mixture was gradually heated to 60°C after 15 minutes. When the suspension temperature reached 40°C or higher, the reaction gradually started, and when the temperature reached 60°C, copper precipitation was clearly observed.
After 30 minutes, the reaction was completed and fine copper powder was precipitated. After filtering with an aspirator, it was washed with acetone and then air-dried at 20°C.

44 g of fine copper powder was obtained, and when the particle size and shape of the powder was observed under an electron microscope, it was a uniform, non-agglomerated, monodispersed spherical powder of 4 μm to 5 μm. The amount of oxygen as an impurity was measured and was found to be very small at 0.10%.

Example 00) Silane coupling agent Vinyl-tris (β-methoxy
Add a mixed solution of 2 g of ethoxy) silane and 3 g of water, stir and mix with a mixer for 10 minutes, then disperse and suspend the entire amount in 500 cc of aqueous solution, then add 50 g of hydrazine l hydrate with stirring, and after 15 minutes. 7
It was gradually heated to 0°C. Suspension at 70°C
After holding for 115 minutes, the reaction was completed and fine copper powder was precipitated.

After filtering with an aspirator, wash with acetone, then
Air dried at °C.

39 g of fine copper powder was obtained, and when the particle size and shape of the powder was observed under an electron microscope, it was a monodisperse spherical powder with a uniform size of 1 μm = 1.5 μm and no agglomeration. As a result of measuring the amount of oxygen as an impurity, it was found to be very small at 0.13χ.

Example 01) Using the same cupric oxide as in Example 0), only the silane coupling agent for surface treatment of the cupric oxide was γ-Glycid.
oxypropyltrimethoxysilane
Copper fine powder was obtained in the same manner as in Example 00) except that the mixed solution was changed to 2 g and 3 g of ethanol.

39g of fine copper powder was obtained, and when looking at the particle size and shape of the powder using an electron microscope, it was a monodisperse spherical powder with a uniform size of 1μm = 1.5μm and no agglomeration, and the oxygen content was also very large at 0.14χ. It was small.

Example 02) Using the same cupric oxide as in Example 00), only a silane coupling agent for surface treatment of cupric oxide was used, 7-Aminop.
Fine copper powder was obtained in the same manner as in Example 00) except that the mixed solution was changed to 2 g of ropyltriethoxysilane and 3 g of ethylene glycol.

39g of fine copper powder was obtained, and when the particle size and shape of the powder was observed using an electron microscope, it was a monodisperse spherical powder with a uniform size of 1μIII to 1.5μm and no agglomeration, and the oxygen content was also very large at 0.15χ. It was small.

〔Effect of the invention〕

As described above, according to the present invention, monodispersed spherical copper fine powder with a narrow particle size distribution can be produced in a short time and at low cost.

The spherical fine copper powder obtained by the present invention is particularly suitable for copper paints that form denser thick film conductors, and is highly pure, so it is also useful for various catalysts.

Claims (4)

[Claims] (1) A method for producing fine copper powder, which comprises coating the surface of copper oxide powder with a silane coupling agent and then reducing the copper oxide powder with hydrazine. (2) Copper oxide powder and a silane coupling agent or an aqueous or alcoholic solution of the silane coupling agent are charged into a mixer or a pulverizer, and the surface of the copper oxide powder is coated with the silane coupling agent by mixing or pulverizing. 2. The method for producing fine copper powder according to claim 1, wherein the copper powder is coated with. (3) A claim characterized in that copper oxide powder coated with a silane coupling agent is dispersed in water, and the copper oxide powder is reduced by adding hydrazine or an aqueous solution of hydrazine while stirring. A method for producing fine copper powder according to item 1 or 2. (4) Add hydrazine or an aqueous hydrazine solution to the copper oxide powder coated with a silane coupling agent dispersed in water while stirring, and then reduce the copper oxide powder by heating this mixed suspension. A method for producing fine copper powder according to claim 3, characterized in that: