Patent ID: 7632710

Claim:
A method for soldering an electronic component on a substrate such that a solder bump formed on the electronic component aligned with an electrode of the substrate is heated and the solder bump thus molten is soldered on the electrode, comprising the steps of: aligning the solder bump of said electronic component with the electrode of the substrate with flux intervening between the solder bump and the electrode, the flux containing metallic powder having a flake or dendrite shape including a core segment of the metal molten at a higher temperature than the liquid phase temperature of solder constituting said solder bump and a surface segment of the metal with good-wettability for said solder molten and to be solid-solved in said core segment molten; heating said electronic component and said substrate to melt said solder bump so that the molten solder is wet and spread along the surface of the metallic powder to reach the electrode; further continuing heating so that the metallic powder remaining without being in contact with said molten solder is molten into substantially spherical shape; and thereafter cooling said substrate and said electronic component so that the molten metallic powder and said solder is solidified.