Flux for solder paste, solder paste and the solder bump, and methods for their preparation

Flux for a solder paste according to the present invention, a resin, a plasticizer, a solvent and a surfactant. Wherein the plasticizer is dibutyl phthalate (dibutylphthalate, DBP), benzyl butyl phthalate (benzylbutylphthalate, BBP), di-octyl phthalate (dioctylphthalate, DOP), dioctyl sebacate (dioctyl sebacate, DOS), and dioctyl Ajay rate (dioctyl azelate, DOZ ) comprises at least one material selected from the group consisting of.