Fine particulate silver powder and production method thereof

Abstract

An object of the present invention is to provide a silver powder which is an unprecedentedly fine particulate silver powder, has a dispersibility more approximate to monodispersibility resulting less aggregation, and has a low impurity content. To achieve the above object, a fine particulate silver powder having unprecedented powder properties in which: a. the average particle diameter DIA of the primary particles obtained by image analysis of a scanning electron micrograph is 0.6 μm or less; b. the crystallite diameter is 10 nm or less; c. the sintering starting temperature is 240° C. or less; and d. the carbon content is 0.25 wt % or less is obtained by allowing a silver ammine complex aqueous solution S1 to flow in a certain flow path (hereinbelow referred to as “first flow path”) providing a second flow path b which joins the first flow path a on its way and allowing an organic reducing agent and additives S2, if required, to flow into the first flow path a through the second first flow path b, and contacting and mixing them at the joining point of the first flow path a and the second flow path b to allow reduction and deposition of particles, and washing the particles with an excess amount of an alcohol.

Description

TECHNICAL FIELD [0001] The invention of this application relates to a fine particulate silver powder and a production method of the fine particulate silver powder. Particularly, the present invention relates to a fine particulate silver powder having a low impurity content. BACKGROUND ART [0002] Conventionally, for the production of a silver powder, wet reduction process has been adopted in which an aqueous solution of silver ammine complex is produced with a silver nitrate solution and ammonia water, and an organic reducing agent is added to this as described in Patent Document 1. In late years, these silver powders are used for forming electrodes and circuits of chip parts, plasma display panel, etc. as main field of application. [0003] [Patent document 1]: Japanese Patent Laid-Open Publication No. 2001-107101 [0004] Therefore, as for such electrodes and circuits, drastic fine production of the electrodes and circuits are demanded, and high reliability has come to be demanded alon...

AI Technical Summary

Benefits of technology

[0008] In the meantime, it has been demanded that the silver powder has a low impurity content. That is to say, the above-mentioned wet reduction process has been adopted for the production of a silver powder and the reducing agent and the like used in the process remain on the surface of the powder particles of the silver powder. Accordingly, this is an inevitable problem as long as the conventional production process is adopted. And as the impurity content increases, the electric resistance of the conductor formed of the silver powder increases.

[0034] The fine particulate silver powder according to the present invention is fine as never present conventionally, has a high dispersibility and has a small impurity content, and it can be understood that such a silver powder is an unprecedented fine particulate silver powder. In addition, it is enabled to efficiently obtain the fine particulate silver powder according to the present invention by adopting the production method described above.

Problems solved by technology

Therefore they were unsuitable for the recent fine-pitched circuit formation, and made a significant factor of decreasing product yield.

In the meantime, the following problems have arisen from a viewpoint of usage of silver powders.

Accordingly, this is an inevitable problem as long as the conventional production process is adopted.

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