An underfilling material for a semiconductor package holding semiconductor elements on a carrier substrate mounted on a circuit board, containing a one pack type thermosetting urethane composition which preferably comprises a urethane prepolymer having a terminal isocyanate group, which is obtained by reacting a polyol with an excessive amount of a polyisocyanate, and a fine powder coated curing {HEAD ~ agent} comprising {TAIL ~ a curing agent} which is in a solid state at room temperature and surface active sites of which are covered with a fine powder 
comprising
An underfilling material for a semiconductor package holding semiconductor elements on a carrier substrate mounted on a circuit board , containing a one pack type thermosetting urethane composition which preferably comprises a urethane prepolymer having a terminal isocyanate group , which is obtained by reacting a polyol with an excessive amount of a polyisocyanate , and a fine powder coated curing { HEAD ~ agent } comprising { TAIL ~ a curing agent } which is in a solid state at room temperature and surface active sites of which are covered with a fine powder
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