| 摘要 |
PROBLEM TO BE SOLVED: To adjust size of solder powder to a predetermined particle size, to achieve a good reproducibility of particle size between different production lots, and to reduce variation in size distribution of the solder powder within a same production lot.SOLUTION: There is provided a solder powder production method that comprises; obtaining a first fluid dispersion of a copper powder having an average particle size of 1 to 24 μm and a size distribution span value of less than 1.0; adding a tin metal salt to the first fluid dispersion to prepare a fluid mixture; adjusting the pH of the fluid mixture to 0.1 to 2.0; adding a reducer to the pH-adjusted fluid mixture and mixing them to obtain a second fluid dispersion in which tin formed by reduction precipitation of tin ion covers the copper powder; and then subjecting the second fluid dispersion to solid-fluid separation, and drying the solid content to obtain a solder powder 10 which is composed of a center core 11 and a coat layer 12 covering the center core 11 and in which the center core 11 is made of copper and an intermetallic compound between copper and tin, and the coat layer 12 are made of tin. In the solder powder 10, an average particle size is 1 to 30 μm, a coefficient of variation of the average particle size is 0.15 or less, and the contained ratio of copper per entire amount of solder powder of 100 mass% is more than 40 mass% and 70 mass% or less.SELECTED DRAWING: Figure 1 |
