Abstract: An additive contains a silicone resin as a deactivation agent which functions at soldering temperature. This novel additive is used for fluxes and soldering pastes. In the course of soldering, the silicone resin in the additive deactivates an activator such as organic acids contained in the flux and the soldering paste in order for removal of an oxide film from a metallic base used for electric circuit. By use of the additive, corrosion of the metallic base with the activator is protected even though the activator remains on the base. The additive enables to omit an unnecessary washing step from a preparation of electric circiut.