JP2002275509A - Method for manufacturing metal powder, metal powder, conductive paste which uses the same and multilayer ceramic electronic parts which use the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing metal powder of fine particles having no coarse particles and little variance in the particle size and to provide the metal powder, a conductive paste which uses the powder, and multilayer ceramic electronic parts which use the powder. SOLUTION: The method for manufacturing metal powder is carried out by incorporating metal salts and a reducing agent into a solvent containing water and having 1>=MΩcm resistivity and reducing the metal salts by the effect of the reducing agent in the mixture liquid in which at least a part of the metal salts or the reducing agent is dissolved in the solvent so as to precipitate the metal powder of the metals included in the metal salts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing metal powder, a metal powder, a conductive paste using the same, and a multilayer ceramic electronic component using the same to form internal electrodes.

[0002]

2. Description of the Related Art Conventionally, a multilayer ceramic electronic component, for example, a multilayer ceramic capacitor, includes a ceramic laminate in which ceramic layers made of a dielectric material are laminated, an internal electrode in a laminated state between ceramic layers, and a ceramic laminate. And terminal electrodes formed at both ends of the terminal.

A conductive paste is used for forming internal electrodes of such a multilayer ceramic electronic component, particularly a multilayer ceramic capacitor. The conductive paste contains a metal powder that functions as a conductive component. As the metal powder, in addition to a noble metal such as silver or palladium, a base metal such as nickel or copper powder has recently been used. In addition, the multilayer ceramic electronic component has been reduced in size and thickness, and accordingly, it has been required to reduce the metal powder contained in the conductive paste used for forming the internal electrodes.

[0004]

However, according to the prior art, when electric conductive impurities are present in water, the conductivity of the water increases. When water containing such impurities is used as a solvent, the impurities serve as nuclei, which facilitates the growth of the particles of the metal powder that precipitates, and the particle diameter varies, and coarse particles may be present in the metal powder. Was. When an internal electrode is formed using a conductive paste containing such a metal powder, coarse particles become convex portions on the coating film on which the conductive paste is printed, and this breaks through the ceramic layers stacked vertically, There has been a problem that the internal electrode layers stacked one above the other via the ceramic layer are short-circuited, and short-circuit failure occurs.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and it is an object of the present invention to provide a method for producing a fine metal powder having no coarse particles and a small variation in particle diameter, a metal powder, and a conductive powder using the same. An object of the present invention is to provide a conductive paste and a multilayer ceramic electronic component using the same.

[0006]

In order to achieve the above object, a method for producing a metal powder according to the present invention has a resistivity of 1 MΩc.
m, a metal salt and a reducing agent are contained in a solvent containing water, and in a mixed solution in which at least a part of the metal salt or the reducing agent is dissolved in the solvent, the metal salt is formed by the action of the reducing agent. Reducing, and depositing a metal powder composed of a metal contained in the metal salt.

The reducing agent solution is preferably at least one selected from the group consisting of hydrazine, hydrazine hydrate, a borohydride compound, and an aminoborazane-based reducing agent.

The metal contained in the metal salt is Pd, C
It is preferably at least one selected from the group consisting of u, Ni, and Ag.

The metal salt is preferably at least one selected from the group consisting of chloride, sulfate and nitrate.

The solvent is preferably a simple substance of water having a resistivity of 1 MΩcm or more, or a mixed solvent of water and an alcohol having a resistivity of 1 MΩcm or more.

[0011] The metal powder of the present invention is characterized by being obtained by the above-described method for producing a metal powder of the present invention.

The conductive paste of the present invention is characterized by containing the above-mentioned metal powder of the present invention and an organic vehicle.

A multilayer ceramic electronic component according to the present invention comprises: a ceramic laminate in which a plurality of ceramic layers are stacked;
And a plurality of internal electrodes formed between the ceramic layers, wherein the internal electrodes are formed using the conductive paste according to claim 7.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION
First, it is characterized in that a solvent containing water having a resistivity of 1 MΩcm or more is used. In the case of a solvent containing water having a resistivity of 1 MΩcm or more, since there are very few electrically conductive impurities which cause an increase in water conductivity, the impurities are unlikely to become nuclei when metal ions are precipitated as metal powder. . Therefore, it is possible to produce a metal powder having a small amount of coarse particles and a substantially uniform particle size.

The metal salt is not particularly limited as long as it can precipitate a metal with a reducing agent.
When used as a conductive component of a conductive paste used for forming internal electrodes of a multilayer ceramic electronic component, Pd, C
at least one selected from the group consisting of u, Ni, and Ag
Preferably it is a seed. Further, the metal salt is preferably one that can be well dissolved in the selected solvent, and is preferably at least one selected from the group consisting of chlorides, sulfates and nitrates.

The reducing agent is not particularly limited as long as it can reduce the metal salt, and examples thereof include hydrazine, hydrazine hydrate, borohydride compounds, and aminoborazane-based reducing agents. In particular, in order to reduce the metal salt to obtain the above-mentioned metal powder, it is more preferable to contain hydrazine hydrate and / or a borohydride compound.

The solvent may be water alone having a resistivity of 1 MΩcm or more, or may be a mixed solvent obtained by further mixing alcohol. Further, the water contained in the solvent having a resistivity of 1 MΩcm or more preferably has a resistivity of about 15 MΩcm.

One embodiment of the method for producing a metal powder according to the present invention will be described below. First, the resistivity is 1MΩ
While stirring a solvent containing water having a diameter of not less than 1 cm, a metal salt is added thereto, and then a reducing agent is added thereto to obtain a mixed solution. The content of the reducing agent is not particularly limited, but is preferably not less than the amount stoichiometrically necessary for reducing the metal salt. Even if the amount of the reducing agent exceeds 10 times the required amount, the excess reducing agent does not contribute to the reduction of the metal salt. Therefore, the content of the reducing agent is preferably within 10 times the required amount. .

Next, the mixed solution is heated to reduce the metal salt by the action of the reducing agent, thereby depositing the metal powder.
The heating temperature is not particularly limited, but is preferably 50 ° C. or higher.

The metal powder of the present invention needs to be obtained by the above-described method for producing a metal powder of the present invention.

The conductive paste of the present invention needs to contain the above-mentioned metal powder of the present invention and an organic vehicle. In addition, it does not prevent containing an organic vehicle and other additives. The organic vehicle is not particularly limited. For example, 25% by weight of an organic binder composed of ethyl cellulose and an alkyd resin and 75% by weight of an organic solvent composed of ethyl carbitol, 1-octanol and a kerosene-based solvent are mixed. And the like.

One embodiment of the multilayer ceramic electronic component of the present invention will be described in detail with reference to FIG. That is, the laminated ceramic electronic component 1 includes a ceramic laminate 2, the internal electrodes 3, and the terminal electrodes 4, and a plated film 5,5 Prefecture.

The ceramic laminate 2 is formed by firing a green ceramic laminate in which a plurality of ceramic layers 2a made of a dielectric material containing BaTiO ₃ as a main component are laminated.

The internal electrodes 3, 3 are located between the ceramic layers 2a in the ceramic laminate 2, and the conductive paste of the present invention is printed on a plurality of green ceramic layers 2a and laminated together with the raw ceramic layers. It is fired at the same time as the raw ceramic laminate, and the respective edges of the internal electrodes 3 are formed so as to be exposed at any end face of the ceramic laminate 2.

The conductive paste is applied to the end face of the ceramic laminate 2 so that the terminal electrodes 4 and 4 are electrically and mechanically joined to one ends of the internal electrodes 3 and 3 exposed on the end face of the ceramic laminate 2. It is applied and baked.

The plating films 5 and 5 are made of, for example, electroless plating such as Sn or Ni, or solder plating, and are formed on the terminal electrodes 4 and 4 in at least one layer.

The material of the ceramic laminate 2 of the multilayer ceramic electronic component of the present invention is not limited to the above-described embodiment, but may be PbZrO ₃ or another dielectric material, insulator, magnetic material, piezoelectric material, or the like. It may be made of a body or a semiconductor material. Further, the number of the internal electrodes 3 of the multilayer ceramic electronic component of the present invention is not limited to the above-described embodiment, and any number of layers may be formed. Further, the plating films 5 and 5 are not necessarily required to be provided, and any number of layers may be formed.

[0028]

(Example 1) In Example 1, nickel is produced as a metal powder, and a multilayer ceramic capacitor is produced as one form of a conductive paste, a test sample and a multilayer ceramic electronic component using the same.

First, as shown in Table 1, the solvent has a resistivity of 0.4 MΩcm, 0.9 MΩcm, and 1.1 MΩcm, respectively.
MΩcm, 2.5MΩcm, 5.0MΩcm, 10.0
Water having MΩcm and 17.0 MΩcm was prepared, and 7 g of nickel chloride as a metal salt was dissolved in 100 ml of the above-mentioned water solvent to prepare a metal salt solution of Samples 1 to 7, 3 g of sodium hydroxide and 80 as a reducing agent. 10 g of hydrazine hydrate was dissolved in 100 ml of the above aqueous solvent to prepare reducing agent solutions of Samples 1 to 7.

Next, the metal salt solution and the reducing agent solution of Samples 1 to 7 were maintained at 60 ° C., and the metal salt solution was added to the reducing agent solution to reduce and precipitate nickel, which was then separated and recovered. After washing with pure water and acetone and drying in an oven, metal powders (nickel) of Samples 1 to 7 were obtained.

Then, the nickel powder of Samples 1 to 7 was observed with a scanning electron microscope, and the particle size was reduced to 30 with a digitizer.
The points were measured, and the average particle diameter and the standard deviation of the particle diameter were determined.

[0032]

[Table 1]

As is clear from Table 1, samples 1 to 7
The average particle size of each sample was excellent in the range of 152 to 158 nm, whereas the standard deviation of samples 1 and 2 in which the resistance value of water as a solvent was less than 1 MΩcm was large at 62 to 65 nm, It can be seen that the standard deviation of samples 3 to 7 having a resistance value of 1 MΩcm or more is small at 14 to 19 nm.

Subsequently, 50% by weight of the metal powder of Samples 1 to 7
And 10 parts by weight of ethylcellulose in terpineol 90
An organic vehicle 40% by weight dissolved in parts by weight and terpineol 40% by weight were mixed and kneaded using a three-roll mill to obtain conductive pastes of Samples 1 to 7.

Therefore, the conductive pastes of Samples 1 to 7 were printed on a glass plate so as to have a coating thickness of 1.0 μm to form an electrode film, and the thickness of the electrode film was measured using a stylus-type film thickness meter. The point surface roughness (Rz) was measured and is summarized in Table 2.

Subsequently, a 1.3 μm thick green ceramic layer containing BaTiO ₃ as a main component is prepared, and one edge of any of the green ceramic layers is formed on the surface of a predetermined number of green ceramic layers. An electrode film to be an internal electrode having a thickness of 0.5 μm after drying is printed so as to be exposed on the end face side, and a predetermined number of these green ceramic layers are laminated and pressed.
100 raw ceramic laminates of Samples 1 to 7 were prepared.

Next, this green ceramic laminate was
_After heating the organic binder at 400 ° C. in an atmosphere of ₂ to burn the organic binder, an oxygen partial pressure of H ₂ —N ₂ — of 9 × 10 ⁻¹² MPa was obtained.
1200 ° C. in a reducing atmosphere composed of H ₂ O gas
Was maintained at the maximum firing temperature for 3 hours to obtain ceramic laminates of Samples 1 to 7. Then, a conductive paste for forming a terminal electrode containing Ag as a conductive component is applied and dried so as to be electrically and mechanically joined to the internal electrodes exposed on the end faces of the ceramic laminates of Samples 1 to 7, and then dried. To form a pair of terminal electrodes, and Ni
A plated film was formed by electrolytic plating, and a Sn plated film was formed on the Ni plated film by electrolytic plating to obtain 100 multilayer ceramic capacitors of Samples 1 to 7.

Therefore, the occurrence of short-circuit failure was measured for 100 multilayer ceramic capacitors of samples 1 to 7 to determine the occurrence of short-circuit failure.
Summarized in In the evaluation, 金属 was given for metal powder and conductive paste falling within the range of the present invention, and x was given for those falling outside the range.

[0039]

[Table 2]

As is apparent from Table 2, the multilayer ceramic capacitors using the metal powders of Samples 3 to 7 having a resistance value of water as a solvent of 1 MΩcm or more had a surface roughness of 59 to 68 nm. 0% short-circuit failure rate
And within the scope of the present invention.

On the other hand, the resistance value of water as a solvent is 1
The electrode films and the multilayer ceramic capacitors using the metal powders of Samples 1 and 2 having a surface roughness of less than 1
28 to 135 nm, and the short-circuit defect occurrence rate is 100
% Was out of the range of the present invention.

Example 2 In Example 2, copper is produced as a metal powder, and a multilayer ceramic capacitor is produced as one form of a conductive paste, a test sample and a multilayer ceramic electronic component using the same.

First, as shown in Table 2, the resistivity of the solvent was 0.4 MΩcm, 0.9 MΩcm, and 1.1 MΩcm, respectively.
MΩcm, 2.5MΩcm, 5.0MΩcm, 10.0
Water having MΩcm and 17.0 MΩcm is prepared, and 50 g of copper sulfate as a metal salt is dissolved in 150 ml of the above-mentioned water solvent to prepare a metal salt solution of Samples 8 to 14, 3 g of sodium hydroxide and hydrogen as a reducing agent are prepared. 20 g of sodium borohydride was dissolved in 150 ml of the above-mentioned aqueous solvent to prepare reducing agent solutions of Samples 8 to 14.

Next, the metal salt solution and the reducing agent solution of Samples 8 to 14 were kept at 60 ° C., and the metal salt solution was added to the reducing agent solution to reduce and precipitate nickel, which was then separated and collected. After washing with pure water and acetone and drying in an oven, metal powders (copper) of Samples 8 to 14 were obtained.

Then, the nickel powders of Samples 8 to 14 were observed with a scanning electron microscope, and the particle size was measured with a digitizer.
The measurement was performed at 0 points, and the average particle diameter and the standard deviation of the particle diameter were obtained.

[0046]

[Table 3]

As is clear from Table 3, samples 8 to 1
The average particle size of Sample No. 4 was excellent in the range of 87 to 92 nm, but the standard deviation of Samples 8 and 9 in which the resistance of water as a solvent was less than 1 MΩcm was large in the range of 51 to 53 nm. Samples 14 to 14 having a resistance value of 1 MΩcm or more
It can be seen that the standard deviation is small at 10 to 13 nm.

Subsequently, 50% by weight of the metal powder of Samples 8 to 14 and 10 parts by weight of ethylcellulose were added to terpineol 9
40 wt% of the organic vehicle dissolved in 0 wt% and 40 wt% of terpineol were mixed and kneaded using a three-roll mill to obtain conductive pastes of Samples 8 to 14.

Therefore, the conductive pastes of Samples 8 to 14 were printed on a glass plate so as to have a coating thickness of 1.0 μm to form an electrode film, and the thickness of the electrode film was measured using a stylus-type film thickness meter. The point surface roughness (Rz) was measured and is summarized in Table 4.

Subsequently, a 1.4 μm thick green ceramic layer containing BaTiO ₃ as a main component is prepared, and one edge of one of the green ceramic layers is formed on the surface of a predetermined number of green ceramic layers. An electrode film to be an internal electrode having a thickness of 0.4 μm after drying is printed so as to be exposed on the end face side, and a predetermined number of these green ceramic layers are laminated and pressed.
100 raw ceramic laminates of Samples 8 to 14 were prepared.

Next, this green ceramic laminate was
_After heating the organic binder at 400 ° C. in an atmosphere of ₂ to burn the organic binder, an oxygen partial pressure of H ₂ —N ₂ — of 9 × 10 ⁻¹² MPa was obtained.
1200 ° C. in a reducing atmosphere composed of H ₂ O gas
Was maintained at the highest firing temperature for 3 hours to obtain ceramic laminates of Samples 8 to 14. Then, a conductive paste for forming a terminal electrode containing Ag as a conductive component is applied and dried so as to be electrically and mechanically joined to the internal electrodes exposed on the end faces of the ceramic laminates of Samples 8 to 14, and dried. To form a pair of terminal electrodes, a Ni plating film is formed on the pair of terminal electrodes by electrolytic plating, and
An Sn plating film was formed on the i-plating film by electrolytic plating, and the multilayer ceramic capacitors of Samples 8 to 14 were formed as 1
00 pieces were obtained.

Therefore, the occurrence of short-circuit defects was determined by measuring the presence or absence of short-circuit defects in 100 multilayer ceramic capacitors of Samples 8 to 14, and the results were evaluated. In the evaluation, 金属 was given for metal powder and conductive paste falling within the range of the present invention, and x was given for those falling outside the range.

[0053]

[Table 4]

As is clear from Table 4, Samples 10 to 1 having a resistance value of water as a solvent of 1 MΩcm or more were obtained.
The multilayer ceramic capacitor using the metal powder of No. 4 had a surface roughness of 47 to 53 nm and an excellent short-circuit defect occurrence rate of 0%, which was within the scope of the present invention.

On the other hand, the resistance value of water as a solvent is 1
The electrode films and multilayer ceramic capacitors using the metal powders of Samples 8 and 9 having a surface roughness of less than 1
08 to 112 nm, and the short-circuit defect occurrence rate is 100
% Was out of the range of the present invention.

[0056]

As described above, according to the present invention, a metal salt and a reducing agent are contained in a solvent containing water having a resistivity of 1 MΩcm or more, and at least a part of the metal salt or the reducing agent is contained. In a mixed solution dissolved in a solvent, a metal salt is reduced by the action of a reducing agent, and a metal powder composed of a metal contained in the metal salt is precipitated, whereby coarse particles are not present. Thus, it is possible to provide a fine metal powder having less variation. Further, by forming an internal electrode using a conductive paste containing such a metal powder, a multilayer ceramic electronic component free from short-circuit failure can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a multilayer ceramic electronic component according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multilayer ceramic electronic component 2 Ceramic body 2a Ceramic layer 3 Internal electrode

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01G 4/12 361 H01G 4/12 361 4/30 301 4/30 301C F-term (Reference) 4K017 AA03 BA02 BA03 BA05 DA01 DA08 EJ01 FB07 5E001 AB03 AH01 AH09 AJ01 AJ02 5E082 AA01 AB03 EE04 EE23 LL02 5G301 DA03 DA06 DA10 DA11 DA42 DA53 DD01

Claims (8)

[Claims] 1. A mixed solution in which a metal salt and a reducing agent are contained in a solvent containing water having a resistivity of 1 MΩcm or more, and at least a part of the metal salt or the reducing agent is dissolved in the solvent. Wherein the metal salt is reduced by the action of the reducing agent to precipitate a metal powder composed of a metal contained in the metal salt. 2. The method according to claim 1, wherein the reducing agent solution is at least one selected from the group consisting of hydrazine, hydrazine hydrate, a borohydride compound, and an aminoborazane-based reducing agent. Production method of metal powder. 3. The method according to claim 2, wherein the metal contained in the metal salt is P
3. The method for producing a metal powder according to claim 1, wherein the metal powder is at least one selected from the group consisting of d, Cu, Ni, and Ag. 4. The method for producing a metal powder according to claim 1, wherein said metal salt is at least one selected from the group consisting of chloride, sulfate and nitrate. . 5. The solvent according to claim 1, wherein the solvent is water alone having a resistivity of 1 MΩcm or more, or a mixed solvent of water and an alcohol having a resistivity of 1 MΩcm or more. 3. The method for producing a metal powder according to item 1. 6. A metal powder obtained by the production method according to claim 1. 7. A conductive paste comprising the metal powder according to claim 6 and an organic vehicle. 8. A multilayer ceramic electronic component comprising: a ceramic laminate in which a plurality of ceramic layers are stacked; and a plurality of internal electrodes formed between the ceramic layers, wherein the internal electrodes are A multilayer ceramic electronic component characterized by being formed using the conductive paste described in (1).