JP2003160804A - Method for manufacturing copper powder, copper powder, electroconductive paste, and laminated ceramic electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a copper powder which is superior in dispersibility and heat contraction and has a high sintering-initiation temperature, to provide the copper powder manufactured by the method, an electroconductive paste using the copper powder and a laminated ceramic electronic component provided with an electrode formed by the use of the conductive paste. <P>SOLUTION: This manufacturing method comprises reducing a raw liquid containing copper salts, calcium compounds and water with a hydrazine-based reducing agent, to precipitate the copper powder containing calcium. A ratio (Ca/(Cu+Ca)) of calcium (Ca) to copper (Cu) in the raw liquid is in a range of 0.05-1.0 wt.%. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention comprises a method for producing a copper powder, a copper powder produced by the production method, a conductive paste using the copper powder, and an electrode formed using the conductive paste. Relates to multilayer ceramic electronic components.

[0002]

2. Description of the Related Art For example, a monolithic ceramic capacitor, which is one of typical monolithic ceramic electronic components, is usually made of a conductive material prepared by mixing and kneading metal powder with an organic vehicle or the like. By printing the paste, a plurality of ceramic green sheets having a predetermined internal electrode pattern formed on the surface are laminated, and ceramic green sheets (outer layer sheet) having no internal electrode pattern are formed on both upper and lower sides thereof. Cut the laminate obtained by stacking and crimping,
After being divided into individual elements, firing is performed, and external electrodes that are electrically connected to the internal electrodes are provided at predetermined positions of the obtained sintered body (multilayer ceramic element).

Conventionally, as a conductive paste used for forming an internal electrode of a monolithic ceramic capacitor or the like, a conductive paste containing a precious metal powder such as palladium or silver as a conductive component has been widely used. Due to these reasons, conductive pastes containing inexpensive base metal powder as a conductive component are now widely used. At present, a conductive paste containing nickel powder as a conductive component is often used, but copper powder is a conductive component that has low electric resistance and can contribute to higher performance of multilayer ceramic electronic components. A part of the conductive paste is being used.

By the way, in recent years, as monolithic ceramic electronic components such as monolithic ceramic capacitors have been miniaturized, in order to secure desired characteristics, it is necessary to form thin and uniform internal electrodes. Therefore, when using a conductive paste containing copper powder as a conductive component, it is necessary to use a copper powder having a uniform particle size and high dispersibility.

Further, as the monolithic ceramic electronic component becomes smaller, defects such as delamination and cracks are more likely to occur due to a mismatch in the sintering of the ceramic and the internal electrode (copper electrode). In particular, copper starts to be sintered. Temperature is 500 ℃
Since the degree is significantly lower than that of ceramics, there is a problem that defects such as delamination and cracks are likely to occur due to sintering mismatch.

Therefore, when an attempt is made to manufacture a small-sized, high-multilayer monolithic ceramic capacitor or the like by using a conductive paste containing copper powder as a conductive component, copper powder is excellent in dispersibility and has a sintering starting temperature. It is necessary to use expensive ones.

Conventional methods for producing copper powder include a powdering method of molten metal, a mechanical pulverizing method, an electrolysis method and a reduction precipitation method. Examples of the reduction precipitation method include, for example, JP-A-57-1553.
No. 02 discloses a method of producing a copper powder by mixing a copper-containing solution containing copper carbonate with hydrazine or a hydrazine compound and heating the mixture. However, since this method is a solid-liquid reaction, the reaction tends to be non-uniform, and it is difficult to obtain a copper powder having high dispersibility.

Further, in Japanese Patent Laid-Open Publication No. 9-256007, a reducing agent is added to a copper-containing solution in which a copper compound and a phosphate coexist to precipitate metallic copper, whereby copper powder having high dispersibility is obtained. A method of obtaining is disclosed. According to this method, it is possible to produce a copper powder having a high dispersibility, but the fact that the sintering temperature peculiar to the copper powder is low has not been solved.

Further, Japanese Patent Laid-Open No. 2000-345201 discloses a method of improving the sintering temperature of copper powder by post-treating the copper powder and fixing an oxide on the surface. However, in the case of this method, the powder is exposed to a considerably high temperature due to frictional heat during the treatment, and there are problems such as oxidation of the copper powder itself, and it is technically difficult and costly. There is a problem that it is disadvantageous.

The present invention solves the above-mentioned problems and is a method for producing a copper powder having excellent dispersibility, a high sintering starting temperature, and excellent heat shrinkage characteristics, and a copper powder produced by the method. Another object of the present invention is to provide a conductive paste using the copper powder, and a laminated ceramic electronic component provided with an electrode formed using the conductive paste.

[0011]

In order to achieve the above object, a method for producing a copper powder according to the present invention (claim 1) comprises a copper salt as a main component, a calcium compound as an accessory component, and water. A step of preparing a raw material liquid containing, a step of preparing a reducing agent aqueous solution containing a hydrazine and / or a hydrazine compound, the raw material solution and the reducing agent aqueous solution are mixed, by performing a reduction reaction And a step of depositing copper powder.

The method for producing a copper powder according to the present invention (claim 1) comprises a raw material liquid containing a copper salt as a main component, a calcium compound as an accessory component, and water, a hydrazine and / or a hydrazine compound. Prepare a reducing agent aqueous solution to be contained, mix the raw material liquid and the reducing agent aqueous solution, and carry out a reduction reaction.
Since the copper powder containing the a component is deposited, the copper powder easily has excellent dispersibility, a high sintering start temperature, and excellent heat shrinkage characteristics simply by mixing the raw material liquid and the reducing agent aqueous solution. Will be able to be manufactured.

As a method of mixing the raw material liquid and the reducing agent aqueous solution to carry out the reduction reaction, for example, basic copper carbonate and a calcium compound are dispersed in pure water, and hydrazine is added to the pure water. After adding the reducing agent aqueous solution dissolved in a constant speed, gradually heated until reaching a predetermined temperature,
An example is a method of holding the temperature for a certain period of time to carry out the reduction reaction.

Further, the detailed mechanism of the fact that the copper powder having excellent dispersibility, high sintering starting temperature and excellent heat shrinkability is obtained by the method of the present invention (claim 1) is not always clear. Although not present, it is speculated that the coexisting calcium (Ca) content suppresses agglomeration and necking between the copper powders during the formation process of the copper powders and dramatically improves the dispersibility of the copper powders.

The Ca content remains in the copper powder, suppresses the sintering of the copper powder, and functions to shift the sintering start temperature (heat shrinkage start temperature) to the high temperature side. Therefore, according to the method for producing a copper powder of the present invention (claim 1) in which the calcium component is added to the raw material liquid containing the copper salt in the liquid phase reduction reaction, the dispersibility is excellent and the sintering starts. It becomes possible to efficiently produce a copper powder having a high temperature and excellent heat shrinkage characteristics. As the copper salt that can be used in the present invention, it is possible to use copper sulfate, copper carbonate, copper chloride, etc., and it is also possible to use other copper salts.

As the calcium compound, it is possible to use calcium carbonate, calcium hydroxide, calcium oxide or the like. The calcium content may be contained in the copper salt as an impurity. When the calcium content is contained in the copper salt as an impurity and the amount does not satisfy the required amount, the calcium content contained in the copper salt as an impurity is added by adding the shortage separately. It is possible to control the total amount of calcium added in relation to copper.

Further, in the method for producing copper powder according to claim 2, when the ratio of copper (Cu) and calcium (Ca) in the raw material liquid is expressed by Ca / (Cu + Ca) (wt%),
It is characterized by being in the range of 0.05 to 1.0% by weight.

Copper (Cu) and calcium (C
When the ratio of a) is represented by Ca / (Cu + Ca) (wt%), by setting it in the range of 0.05 to 1.0 wt%, the dispersibility is excellent, the sintering start temperature is high, and the heat It is possible to reliably produce a copper powder having excellent shrinkage characteristics.

Ca / (Cu + Ca) (% by weight)
Is preferably in the range of 0.05 to 1.0% by weight, because when Ca / (Cu + Ca) is less than 0.05% by weight, the dispersibility of the obtained copper powder becomes insufficient. Instead, the amount of Ca remaining in the copper powder decreases,
Sufficient sintering suppression effect cannot be obtained, and Ca /
This is because even if the content of (Cu + Ca) is increased in the range of more than 1.0% by weight, no remarkable improvement is observed in the effect of making the copper powder finer, more dispersed, or suppressing sintering.

The copper powder of the present invention (claim 3) is
It is manufactured by the method for manufacturing a copper powder according to claim 1 or 2.

The copper powder of the present invention (Claim 3) is produced by the method for producing a copper powder according to Claim 1 or 2, and has excellent dispersibility, high sintering initiation temperature, and heat shrinkage. Due to its excellent characteristics, by using the copper powder of the present invention as a conductive component of a conductive paste, it is possible to reduce shrinkage at the time of sintering when used for manufacturing a small-sized, high-stack-number multilayer ceramic electronic component. Thus, it is possible to obtain a highly reliable laminated ceramic electronic component having a good shape accuracy and having uniform internal electrodes.

Further, the conductive paste of the present invention (claim 4) is characterized by containing the copper powder according to claim 3 and an organic vehicle.

In the conductive paste of the present invention (claim 4), the copper powder having excellent dispersibility, high sintering start temperature and excellent heat shrinkage property according to claim 3 is used as a conductive component. Therefore, when the conductive paste of the present invention is used for manufacturing a small-sized, high-lamination number multilayer ceramic electronic component, shrinkage during sintering is small, shape accuracy is good, and a uniform internal electrode is provided. It is possible to obtain a highly reliable laminated ceramic electronic component.

The laminated ceramic electronic component of the present invention (Claim 5) has a structure in which internal electrodes, which are sintered bodies of the conductive paste according to Claim 4, are arranged between the ceramic layers. It is characterized by that.

The multilayer ceramic electronic component of the present invention (Claim 5) is provided with the internal electrode which is the sintered body of the conductive paste according to Claim 4, and the internal electrode has a small shrinkage during sintering. Since the shape accuracy is good and the shape is uniform, it is possible to provide a highly reliable multilayer ceramic electronic component having desired characteristics.

[0026]

EXAMPLES The present invention will be specifically described below by showing Examples of the present invention.

Example 1 (1) As a copper salt, 200 g of basic copper carbonate containing different amounts of calcium impurities was dispersed in 2300 mL of pure water at 30 ° C. to prepare a raw material liquid. (2) Also, 200 g of hydrazine, which is a reducing agent, was added to pure water 3
A reducing agent aqueous solution (hydrazine aqueous solution) was prepared by dissolving it in 00 mL. (3) Then, the reducing agent aqueous solution was added to the raw material liquid at 13 mL / min.
At a constant rate, the mixture was gradually heated so as to reach 90 ° C. in 90 minutes, and held at 90 ° C. for 60 minutes to carry out a reduction reaction to precipitate a reduction product (copper powder). (4) Next, after the copper powder is separated and washed, it is further put into pure water, sedimentation separation is repeated several times, washed with acetone, and then dried by a vacuum dryer to obtain copper. A powder was obtained.

Example 2 (1) 200 g of basic copper carbonate having a calcium impurity content of 0.005% by weight was dispersed in 2300 mL of pure water at 30 ° C., and 0 to 7.4 g of calcium carbonate was added. The raw material liquid was prepared by adding and dispersing in the range of. (2) Also, 200 g of hydrazine, which is a reducing agent, was added to pure water 30
A reducing agent aqueous solution (hydrazine aqueous solution) was prepared by dissolving it in 0 mL. (3) Then, the reducing agent aqueous solution was added to the raw material liquid at 13 mL / min.
At a constant rate, the mixture was gradually heated so as to reach 90 ° C. in 90 minutes, and held at 90 ° C. for 60 minutes to carry out a reduction reaction to precipitate a reduction product (copper powder). (4) Next, after the copper powder is separated and washed, it is further put into pure water, sedimentation separation is repeated several times, washed with acetone, and then dried by a vacuum dryer to obtain copper. A powder was obtained.

[Characteristic Evaluation of Copper Powders Obtained in Examples 1 and 2] The primary particle diameters of the copper powders obtained in Examples 1 and 2 were measured. It was confirmed that the surface area was about 0.9 m ² / g and was substantially constant.

Further, the particle size distributions of the copper powders obtained in Examples 1 and 2 above were measured using a laser diffraction type particle size distribution meter. The result is shown in FIG.

From FIG. 1, the ratio of Ca in the copper powder Ca / (C
It can be seen that the value of the particle size distribution decreases as the amount of (u + Ca) increases, and that by increasing the Ca ratio Ca / (Cu + Ca), the aggregation of the copper powders is improved and the dispersibility is improved. Further, from FIG. 1, in order to sufficiently improve the dispersibility, the ratio of Ca is Ca / (Cu + Ca)
It can be seen that it is desirable to set the content to 0.05% by weight or more.

Further, from FIG. 1, the ratio of Ca Ca / (Cu
It can be seen that the effect of improving the dispersibility is hardly increased even if + Ca) is increased in the region exceeding 1.0% by weight. From this, the ratio of Cu and Ca Ca / (Cu + C
It is understood that the content of a) is preferably in the range of 0.05 to 1.0% by weight.

The ratio of Cu and Ca in the raw material liquid Ca /
(Cu + Ca) and Cu / Ca ratio Ca / (Cu + Ca) in the obtained copper powder were examined. The result is shown in FIG. From FIG. 2, the ratio of Cu and Ca in the raw material liquid Ca / (C
u + Ca) and the ratio of Ca in the obtained copper powder Ca / (C
u + Ca) is almost the same, and it can be seen that the total amount of Ca in the raw material liquid is precipitated together with the copper powder.

Further, regarding the obtained copper powder, TMA
The sintering start temperature was measured using (thermo-mechanical analysis). The result is shown in FIG. From FIG. 3, the ratio of Ca Ca / (Cu
It was confirmed that the sintering start temperature increased as + Ca) increased. Further, from FIG. 3, the proportion C of Ca
It can be seen that even if a / (Cu + Ca) is increased in the region exceeding 1.0% by weight, the effect of improving the sintering start temperature is hardly increased.

From these data, the ratio of Cu to Ca, C
It is understood that a / (Cu + Ca) is preferably in the range of 0.05 to 1.0% by weight.

[Embodiment 3] The copper powder (the ratio of Cu to Ca, Ca / (Cu + Ca)) obtained in the above Embodiment 1 is 0.5.
A conductive paste containing a copper powder in a weight percentage) as a conductive component was prepared, and this conductive paste was used to manufacture a laminated ceramic capacitor as shown in FIG.

As shown in FIG. 4, the monolithic ceramic capacitor according to the third embodiment includes a ceramic capacitor element (multilayer body) 1, a plurality of internal electrodes 2 for obtaining electrostatic capacitance, and a dielectric ceramic. The layers 3 are alternately laminated, and the internal electrodes 2 are alternately drawn out to the opposite ends of the laminated body 1, and both ends of the ceramic capacitor element 1 are electrically connected to the predetermined internal electrodes 2. It has a structure in which external electrodes 4a and 4b are disposed.

The method of manufacturing this laminated ceramic capacitor will be described below. (1) Copper powder produced in Example 1, that is, Cu
A copper powder having a Ca / (Cu + Ca) ratio of 0.5% by weight was mixed with an ethyl cellulose resin and terpineol to prepare a conductive paste. (2) Then, this conductive paste is printed on a dielectric sheet (ceramic green sheet) having a thickness of about 7.5 μm and containing barium titanate-based ceramic as a main component, and an internal electrode pattern (electrode layer) is formed on the surface. An electrode-arranged sheet was formed. (3) Next, this electrode-disposed sheet is laminated, 100 layers of electrode layers and dielectric layers are alternately stacked, and further, a ceramic green sheet in which no electrode layers are disposed on both upper and lower surfaces (outer layer sheet) Was laminated, pressure-bonded, cut, subjected to binder removal treatment, and then fired in a reducing atmosphere. (4) Then, by applying a conductive paste for forming an external electrode and firing it at a predetermined position of the laminated body after sintering, an external electrode that is electrically connected to the internal electrode is formed. A monolithic ceramic capacitor as shown was obtained. The dimensions of the monolithic ceramic capacitor produced in Example 3 are 3.2 mm in length × 1.6 mm in width × 1.2 mm in thickness.

It was confirmed that the monolithic ceramic capacitor manufactured in Example 3 had a small shrinkage during sintering, had a good shape accuracy, was equipped with uniform internal electrodes, and had desired characteristics. It was

In Example 3, the multilayer ceramic capacitor was manufactured by using the conductive paste containing the copper powder manufactured by the method of the present invention. However, it contains the copper powder manufactured by the method of the present invention. The conductive paste can be applied to multilayer ceramic electronic components other than the multilayer ceramic capacitor (for example, multilayer LC composite components, multilayer inductors, multilayer substrates, etc.).

In other respects, the present invention is not limited to the above-mentioned examples, and a raw material solution containing a copper salt, a calcium compound and water is reduced by a hydrazine reducing agent. With regard to specific conditions and operating methods for depositing copper powder, various applications and modifications can be made within the scope of the invention.

[0042]

As described above, the method for producing copper powder according to the present invention (Claim 1) comprises a raw material liquid containing a copper salt as a main component, a calcium compound as a secondary component, and water. Since a reducing agent aqueous solution containing hydrazine and / or a hydrazine compound is prepared, a raw material solution and a reducing agent aqueous solution are mixed, a reduction reaction is performed, and copper powder containing Ca is deposited. By mixing the raw material liquid and the reducing agent aqueous solution, it becomes possible to easily produce a copper powder having excellent dispersibility, a high sintering start temperature, and excellent heat shrinkage characteristics.

Further, as in the method for producing a copper powder according to claim 2, the ratio Ca / (C) of copper (Cu) and calcium (Ca).
(u + Ca) in the range of 0.05 to 1.0% by weight makes it possible to reliably produce a copper powder having excellent dispersibility, a high sintering start temperature, and excellent heat shrinkage characteristics. .

The copper powder of the present invention (claim 3) is
It is manufactured by the method for manufacturing a copper powder according to claim 1 or 2, and has excellent dispersibility, a high sintering start temperature,
Since it has excellent heat shrinkage characteristics, by using the copper powder of the present invention as a conductive component of a conductive paste, a small size,
When used to manufacture a high number of laminated ceramic electronic components, it is possible to obtain a highly reliable multilayer ceramic electronic component with less shrinkage during sintering, good shape accuracy, and uniform internal electrodes. become.

Further, in the conductive paste of the present invention (claim 4), copper powder having excellent dispersibility, high sintering starting temperature and excellent heat shrinkage property according to claim 3 is used as a conductive component. Therefore, when the conductive paste of the present invention is used in the production of a small-sized, high-lamination number monolithic ceramic electronic component, shrinkage during sintering is small, the shape accuracy is good, and a uniform internal electrode is formed. It is possible to obtain a highly reliable multilayer ceramic electronic component provided with the electronic component.

Further, the multilayer ceramic electronic component of the present invention (Claim 5) is provided with an internal electrode which is a sintered body of the conductive paste according to Claim 4, and the internal electrode shrinks during sintering. It is possible to provide a highly reliable monolithic ceramic electronic component having desired characteristics because it has a small amount, good shape accuracy, and is uniform.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a Ca content and a copper powder particle size distribution D50 (μm).

FIG. 2 Ratio of Ca in raw material liquid Ca / (Cu + Ca)
And the ratio of Ca in the obtained copper powder Ca / (Cu + Ca)
It is a figure which shows the relationship of.

FIG. 3 is a diagram showing the relationship between the ratio Ca / (Cu + Ca) of Ca in copper powder and the sintering start temperature.

FIG. 4 is a cross-sectional view schematically showing a monolithic ceramic capacitor manufactured using a conductive paste containing copper powder manufactured by a method according to an embodiment of the present invention.

[Explanation of symbols]

1 Ceramic capacitor element (multilayer body) 2 internal electrodes 3 Dielectric ceramic layer 4a, 4b external electrodes

Claims (5)

[Claims] 1. A step of preparing a raw material liquid containing a copper salt as a main component, a calcium compound as a subcomponent, and water, and a step of preparing an aqueous reducing agent solution containing hydrazine and / or a hydrazine compound. And a step of precipitating copper powder by mixing the raw material liquid and the reducing agent aqueous solution and performing a reduction reaction. 2. The ratio of copper (Cu) and calcium (Ca) in the raw material liquid is in the range of 0.05 to 1.0 wt% when expressed by Ca / (Cu + Ca) (wt%). The method for producing copper powder according to claim 1, wherein the copper powder is present. 3. A copper powder produced by the method for producing a copper powder according to claim 1 or 2. 4. A conductive paste containing the copper powder according to claim 3 and an organic vehicle. 5. A laminated ceramic electronic component, wherein the internal electrode, which is a sintered body of the conductive paste according to claim 4, has a structure arranged between ceramic layers.