| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing fine spherical metal grains with superior economical efficiency because no satisfactory methods for economically producing spherical metal grains for bumps having 10μm to 1 mm diameter have so far been provided yet. SOLUTION: Pieces of metal, obtained, e.g. by blanking a tape-shaped metal foil, rolled to prescribed thickness, with a die or cutting it into prescribed size or cutting an extra fine metal wire having <=0.1 mm diameter into prescribed size, are passed through an oxyhydrogen flame and melted in it. After being passed through the oxyhydrogen flame, the molten metal pieces are cooled and solidified, by which spherical grains having 10μm to 1 mm diameter are obtained. A burner with a simple duplex-tube structure suffices for a burner for producing oxyhydrogen flame, and an oxyhydrogen flame is formed at the tip of the burner by supplying oxygen and the metal pieces through the inside tube and supplying hydrogen through the outside tube. Moreover, a pressure slightly higher than atmospheric pressure suffices for the supply pressure of oxygen and hydrogen, and also the amount of oxygen and hydrogen to be supplied can be reduced to the minimam at which the burning of the oxyhydrogen flame can be continued with stability.
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