Patent 7909908 was granted and assigned to DOWA Electronics Materials Co., Ltd. on March, 2011 by the United States Patent and Trademark Office.
A copper powder that is excellent in weatherability and adapted for use in conductive paste is provided that contains 10-20,000 ppm, preferably 100-2,000 ppm, of Sn. The copper powder is particularly preferably one having an average particle diameter DM of 0.1-2 μm and, further, one wherein the particle diameter of at least 80% of all particles is in the range of 0.5 DM-1.5 DM. This copper powder can be produced, for example, by precipitating Cu metal by reduction of Cu ions in the presence of Sn ions.