The present invention relates to variable melting point solder formulations. The solder is comprised of at least one base metal or base metal alloy, preferably alloyed with at least one melting point depressant metal, such that the solidus point of the solder composition is reduced to an initial solidus temperature. Said base metal or base metal alloy, alloyed with at least one melting point depressant metal is mixed with at least one additive metal or additive metal alloy. When heated to a process temperature above said initial solidus temperature, a reaction occurs between the melting point depressant metal, and the additive metal, such that solidification occurs at the process temperature via the formation of intermetallic phases, effectively increasing the solidus of the base metal, and of the overall solder.