METHOD FOR PRODUCING METAL POWDER AND SOLDER PASTE USING METAL POWDER OBTAINED BY THE METHOD

PROBLEM TO BE SOLVED: To provide a simple method for collecting a metal powder which is suitable for use as a fine-pitch solder powder and has a volume-cumulative median diameter D50in the range of 1-5 μm, at a high yield. SOLUTION: When producing the metal powder having the volume-cumulative median diameter D50of 1-5 μm by mixing a first aqueous solution containing a cation of a base metal with a second aqueous solution containing a divalent chromium ion to cause a reduction reaction therebetween, this method includes: introducing each tip part of first and second supply pipes 12a and 12b into the inside of a reaction vessel 11; arranging each of the tips in parallel at a fixed height from the inner bottom of the vessel with a spacing between the tips; introducing the first aqueous solution and the second aqueous solution from the first supply pipe and the second supply pipe into the vessel at a fixed flow rate to bring both of the aqueous solutions in contact with each other in the vessel; thereby causing the reduction reaction between the solutions to generate nuclei of the metal powder; also retaining a mixture of both of the aqueous solutions in the vessel for a fixed period of time while holding a liquid level 11c at a fixed height to grow the nuclei of the metal powder, which have been formed through the reduction reaction; and then discharging the mixture of both of the aqueous solutions from the bottom of the vessel at a fixed flow rate. COPYRIGHT: (C)2011,JPO&INPIT