soldering flux includes : a solvent of which solubility in water is more than 0 . 01 % by weight and less than 6 . 8 % by weight ; an organic acid component ; and amine counteracting the organic acid component . a solubility of the amine in water is more than 5 . 0 % by weight , and the amine is able to be linked to a conductive metal via a coordination linkage . a solder bump is formed by heating a solder ball with the soldering flux . the residue of the flux on the surface of the solder bump has water solubility , and is easily eliminated . further , the conductive metal coordinated to the amine is deposited on the surface of the solder bump by water washing . as a result , when testing the semiconductor device having the solder bump 7 by a contact pin contacting with the solder bump , the contact pin is prevented from contamination , the contact pin is certainly contacted with the solder bump , and the semiconductor device is accurately tested .