JP3141669B2 - Production method of silver / palladium powder - Google Patents

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 a silver / palladium powder required for producing a conductive paste used for forming an internal electrode of a laminated electronic component or a multilayer substrate.

[0002]

2. Description of the Related Art Conventionally, as an example of a laminated electronic component, a chip-type porcelain capacitor, which has been in great demand for satisfying the requirements of small size and large capacity relatively easily, has been known. When manufacturing such a capacitor, a ceramic green (raw) sheet having a conductive paste for forming an internal electrode applied on its surface is stacked on each other, and then a laminate is formed by pressing the sheets together. This laminate is divided into predetermined shapes and sizes to obtain unfired chip bodies, and a conductive paste for forming an external electrode is applied to each chip body, followed by firing of a ceramic green sheet. And a method in which the conductive paste is baked simultaneously.

In this case, as a conductive paste for forming an internal electrode, silver (Ag) powder and palladium (Pd) powder, both of which are commercially available, are each dissolved in a terpineol-based vehicle, that is, ethyl cellulose is dissolved in terpineol. It is a common practice to use an organic vehicle that is added to the resulting organic vehicle and then dispersed.

[0004]

When a chip body on which an internal electrode pattern made of a conductive paste having the conventional composition is formed is fired, delamination (delamination) frequently occurs. As a result, the product yield rate was to be reduced. It is considered that such inconvenience occurs because the Pd powder constituting the conductive paste together with the Ag powder undergoes oxidative expansion under a predetermined temperature condition.

That is, Ag powder, which is a single component, and Pd
The thermal expansion coefficient of the mixed powder obtained by mixing the powder and
In addition to the mixing ratio of Pd powder to powder, FIG.
3 and the mixing ratio of Ag and Pd is 95% by weight: 5.
As shown in FIG.
In the vicinity, thermal expansion of up to about 4% occurs. FIG. 2 shows a case where the mixing ratio of Ag and Pd is 70% by weight: 30% by weight, and FIG. 3 shows a case where the mixing ratio of both is 30% by weight: 70% by weight. In each case, it is clear that significant thermal expansion of the mixed powder occurs due to oxidative expansion of the Pd powder.

The present invention has been made in view of such inconvenience, and has no occurrence of delamination.
It is an object of the present invention to provide a method for producing a silver / palladium powder capable of obtaining a conductive paste capable of improving the product yield.

[0007]

According to the method of the present invention for producing silver / palladium powder, in order to achieve the above object, formalin is added to a solution of glycols in which silver nitrate and palladium nitrate are dissolved. Thereafter, the obtained mixed solution is subjected to a heat reduction treatment.

[0008]

Embodiments of the present invention will be described below. In the following description, inductors and capacitors are manufactured using a conductive paste made of silver / palladium powder manufactured according to the method of the present invention, but other multilayer electronic components and multilayer substrates are used. Naturally, the method of the present invention can be applied.

First Embodiment The method of the present invention is to add silver / palladium by adding formalin to a solution of glycols in which silver nitrate and palladium nitrate are dissolved, and then subjecting the resulting mixed solution to a heat reduction treatment. This is a method for producing powder,
In Examples, the mixing ratio of Ag and Pd is 95% by weight: 5.
A procedure for producing the silver / palladium powder in which the weight percentage is set will be described.

First, 125 g of silver nitrate and 9 g of palladium nitrate were prepared, and they were added and dissolved in a glycol solution solution consisting of 1000 ml of ethylene glycol and 100 ml of water.
Add enough ml of formalin and stir well. Subsequently, the obtained mixed solution is subjected to a heat-reduction treatment, that is, a heat-reduction treatment which means that the mixture is reduced at a temperature of 170 ° C. for one hour. Then, silver / palladium powder is co-precipitated in this mixed solution, and the co-precipitated silver / palladium powder is 95% by weight A
g: 5% by weight Pd.

Therefore, the silver / palladium powder is recovered by filtration, and the recovered silver / palladium powder is washed with water and then dried at a temperature of 90 ° C. to obtain the desired mixing ratio. Silver / palladium powder was obtained. Furthermore, according to the inventors of the present invention measuring the coefficient of thermal expansion of the silver / palladium powder manufactured according to such a procedure, the coefficient of thermal expansion was as shown by the solid line in FIG. In the case of the conventional example in which the Ag powder and the Pd powder, which are simple components, are merely mixed, that is, the oxidation expansion as in the case of the conventional example represented by the broken line in FIG. It is clear that this will not happen.

Subsequently, the inventor of the present invention conducted a comparative study on the occurrence of delamination when using the conductive paste made of the silver / palladium powder obtained as described above. The results will be described.

First, 95% by weight was obtained in order to obtain a research sample (hereinafter referred to as a developed product) prepared according to the method of the present invention.
Ag: A conductive paste is prepared by dispersing 50 parts by weight of a silver / palladium powder having a mixing ratio of 5% by weight of Pd in 50 parts by weight of a terpineol-based vehicle, and then an internal electrode pattern made of the conductive paste is prepared. A 30-μm-thick ferrite ceramic green sheet having 30 μm formed thereon was stacked and pressure-bonded to produce a laminate. Furthermore, after dividing this laminated body to obtain 100 chip bodies, these chip bodies were fired at a temperature of 900 ° C. for 2 hours to produce an inductor as a development product. When the presence or absence of delamination was examined in these developed products, it was confirmed that no delamination occurred.

A conductive paste is prepared by dispersing a mixed powder obtained by sufficiently mixing 45 parts by weight of Ag powder and 5 parts by weight of Pd powder in 50 parts by weight of the same terpineol-based vehicle. By following the same procedure, a test sample (hereinafter, referred to as a conventional product) as a comparative example having the same configuration was prepared. When the presence or absence of delamination was examined in these conventional products, it was confirmed that delamination occurred in 63 out of 100 pieces. That is, this comparative study also shows that the developed product is superior to the conventional product.

Second Embodiment In this second embodiment, a procedure for producing a silver / palladium powder in which the mixing ratio of Ag and Pd is 70% by weight: 30% by weight will be described.

First, 135 g of silver nitrate and 81 g of palladium nitrate were prepared, and these were mixed with 100 g of propylene glycol.
After dissolving in 0 ml, 50 ml of formalin is added. Then, while heating at a temperature of 120 ° C., 1
A heat reduction treatment, which means reducing over time, is added to the resulting mixed solution. Then, silver / palladium powder is co-precipitated in this mixed solution, and the co-precipitated silver / palladium powder is 70% by weight A
g: 30% by weight Pd.

Then, the silver / palladium powder is recovered, washed with water, and then dried at a temperature of 90 ° C., so that a silver / palladium powder having a desired mixing ratio is obtained. Further, according to the measurement of the coefficient of thermal expansion of the obtained silver / palladium powder, the coefficient of thermal expansion shows a change represented by a solid line in FIG. It has been confirmed that the oxidative expansion unlike the conventional example represented by the imaginary line does not occur.

Subsequently, 70% by weight of Ag: 30% by weight of P
After preparing a conductive paste obtained by dispersing 50 parts by weight of silver / palladium powder having a mixing ratio of d in 50 parts by weight of a terpineol-based vehicle, the thickness at which the internal electrode pattern made of the conductive paste is formed is formed. A laminate was produced by stacking 50 barium titanate-based ceramic green sheets of 10 μm and pressing them together. Further, after dividing the laminated body to obtain 100 chip bodies, the chip bodies are fired at a temperature of 1150 ° C. for 2 hours to produce a capacitor as a development product, and then delamination. When the presence or absence of occurrence was examined, no occurrence of delamination was observed in these developed products.

A comparative example was prepared by preparing a conductive paste in which a mixed powder consisting of 35 parts by weight of Ag powder and 15 parts by weight of Pd powder was dispersed in 50 parts by weight of a terpineol-based vehicle. When a sample for use (hereinafter referred to as a conventional product) was prepared, 10
The occurrence of delamination was observed in 35 out of 0 pieces.
In other words, this comparative study also reveals the superiority of the developed product over the conventional product.

Third Embodiment In this third embodiment, a procedure for producing a silver / palladium powder in which the mixing ratio of Ag and Pd is 30% by weight: 70% by weight will be described.

First, 12 g of silver nitrate and 3 palladium nitrate
8g, prepare ethylene glycol 1000m
and 10 ml of formalin was added thereto, and the resulting mixed solution was subjected to a heat reduction treatment, that is, 1
A heat reduction treatment is performed, which means that the reduction is performed at a temperature of 30 ° C. for 1 hour. Then, silver / palladium powder having a mixing ratio of 30% by weight of Ag: 70% by weight of Pd is co-precipitated in the mixed solution, and the co-precipitated silver / palladium powder is recovered by filtration. When the recovered silver / palladium powder is washed with water and dried at a temperature of 90 ° C., a silver / palladium powder having a desired mixing ratio is obtained.

According to the measurement of the coefficient of thermal expansion of the obtained silver / palladium powder, the coefficient of thermal expansion shows a change as shown by the solid line in FIG. Oxidative expansion unlike the conventional example represented by the imaginary line in FIG. 3 does not occur at all. Therefore, it is clear that the silver / palladium powder obtained in this example can be said to be useful in producing a conductive paste for forming an internal electrode such as a laminated electronic component or a multilayer substrate.

[0023]

As described above, according to the present invention, there is provided a silver / silver alloy.
According to the method for producing palladium powder, it is possible to produce silver / palladium powder that does not undergo oxidative expansion even under a predetermined temperature condition. Therefore, even when the conductive paste containing the silver / palladium powder is used for forming internal electrodes such as a multilayer electronic component or a multilayer substrate, delamination does not occur and the product yield is improved. Is obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a change in the coefficient of thermal expansion when the mixing ratio of Ag and Pd is 95% by weight: 5% by weight.

FIG. 2 is an explanatory diagram showing a change in the coefficient of thermal expansion when the mixing ratio of Ag and Pd is 70% by weight: 30% by weight.

FIG. 3 is an explanatory diagram showing a change in coefficient of thermal expansion when a mixing ratio of Ag and Pd is 30% by weight: 70% by weight.

Claims (1)

(57) [Claims] 1. A method for producing a silver / palladium powder, comprising adding formalin to a solution of glycols in which silver nitrate and palladium nitrate are dissolved, and then subjecting the resulting mixed solution to a heat reduction treatment. .