FLUX ACTIVATOR AGENT, FLUX, AND SOLDER

An object is to provide a flux activator, a flux, and a solder which can improve the solder wettability immediately after soldering and can continuously improve the solder wettability. Contained is a halogen compound represented by formula I below, where X 1 and X2 represent different halogen atoms, R1 and R2 are a group represented by a formula - OH, -0 R3, -0-C(=O)-R4, or -0-C(=O)-NH-R5 and optionally represent the same group or different groups, and R3, R4, and R5 are an aromatic hydrocarbon group or an aliphatic hydrocarbon group having 1 to 18 carbon atoms and optionally represent the same group or different groups.