PURPOSE: To obtain a solder paste capable of preventing flux spread at preheating by adding the specified quantity of fluoric compound.

CONSTITUTION: The fluoric compound of 0.05-10wt.% is added in the flux of solder paste, which powder solder and liquid or paste flux are mixed. The fluoric compound is composed of a fluoric resin compound and fluoric surface active agent. A content of the fluoric compound under 0.05wt.% caused a slump of the solder paste, over 10wt.% impairs solderability. Thus, this prevents the printed shape of solder paste from destroying by preheating at soldering and the generation of a slump phenomenon, so as to be effective in preventing bridge between leads and the generation of soldering hole.