Copper flake powder, method for producing copper flake powder, and conductive paste using copper flake powder

Abstract

The present invention is mainly for providing a flake copper powder for a conductive paste with particle properties which are defined by that the particle thickness is thinner being possible for use to form an electrode or a circuit, and a production process thereof. To achieve the object of producing the following particles, each powder particles shape is plastically processed into a flake-shape, wherein the flake copper powder has a cumulative particle diameter D 50 of 10 μm or smaller measured with laser diffraction scattering particle size distribution method. The D 10 , D 50 and D 90 measured with the laser diffraction scattering particle size distribution method are illustrative and the SD/D 50 value measured by the standard deviation of particle distribution with the laser diffraction scattering particle size distribution, is 0.55 or larger and/or a D 90 /D 10 of 4.5 or smaller. The flake copper powder is compressed with a high energy ball mill whose media beads having fine particle diameter which plastically deforms the copper particles into flake-shaped particles, so that stable flake copper powder is produced.

1 . Flake copper powder processed by plastic deformation of each of particles of copper powder characterized in that: 
 a cumulative particle diameter D 50  is 10 μm or smaller;    a SD/D 50  value is 0.55 or smaller; and    a D 90 /D 10  value is 4.5 or smaller;    in which SD is a standard deviation of a particle distribution measured by a laser diffraction scattering particle size distribution method, and D 10 , D 50  and D 90  are cumulative particle diameters measured thereby.    
   
   
       2 . The flake copper powder according to  claim 1 , wherein an aspect ratio (average major axis/average thickness) of said powder particle is from 3 to 200.  
   
   
       3 . The flake copper powder according to  claim 1 , wherein Dmax/D 50  of a ratio of a cumulative particle diameter D 50  to the maximum cumulative particle diameter Dmax by the laser diffraction scattering particle size distribution method is 5 or smaller.  
   
   
       4 . Flake copper powder including said flake copper powder according to  claim 1  by 70 wt % or larger in existence rate.  
   
   
       5 . A manufacturing method of the flake copper powder according to  claim 1  comprising the steps of: 
 dispersing a copper powder under an agglomerate condition;    using the copper powder having superior dispersity whose agglomerate degree is 1.6 or smaller after completion of dispersion; and    forming and plastically deforming particles of said copper powder in a flake manner by compressing said particles of said copper powder with a high energy ball mill using media beads, each whose particle diameter is 0.5 mm or smaller.    
   
   
       6 . The manufacturing method of flake copper powder according to  claim 5  wherein a gravity of each of the media beads is from 3.0 g/cm 3  to 6.5 g/cm 3 .  
   
   
       7 . A conductive paste produced using said flake copper powder according to  claim 1.