Patent ID: 7743966

Claim:
A method for bonding a semiconductor element, which includes reflow-bonding a solder bump formed on a first substrate to an electrode formed on a second substrate, comprising: applying a soldering flux to be used in reflow-bonding the solder bump formed on the first substrate to the electrode formed on the second substrate, comprising: a first thermosetting resin, a polyhydric alcohol and an organic acid, the soldering flux not including a curing agent or a cure catalyst; reflow-bonding the solder bump to the electrode with the soldering flux which is not cured while melting the solder bumps without curing the first thermosetting resin thereby keeping the soldering flux uncured; filling an underfill material between the first substrate and the second substrate with the soldering flux which is not cured being left, the underfill material including a second thermosetting resin of the same group as the first thermosetting resin and at least one of a curing agent and a cure catalyst for curing the first and the second thermosetting resins; and after filling an underfill material to compatibly mix the first and the second thermosetting resins, heating to cure the first and the second thermosetting resins compatibly mixed with each other.