EP 3 800 003 A1 by a following Formula (1).  [Concept 2] [0014] A rosin-modified product may be produced by a reaction of a rosin or a rosin derivative, an organic acid and an alkanolamine. [Concept 3] [0015] A flux composition may comprise the rosin-modified product according to Concept 1 or 2. [Concept 4] [0016] The flux composition according to Concept 3 may further comprise a reactant of two molecules of alkanolamine. [Concept 5] [0017] In the flux composition according to Concept 3 or 4, a mixing amount of the rosin-modified product may be 5% by weight to 65% by weight based on a total amount of a flux. [Concept 6] [0018] The flux composition according to any one of Concepts 3 to 5 may further comprise a phosphoric acid ester or a phosphonic acid ester, wherein a mixing amount of the phosphoric acid ester or the phosphonic acid ester may be 1.0% by weight to 15% by weight based on a total amount of a flux. [Concept 7] [0019] The flux according to any one of Concepts 3 to 6 may further comprise an organic acid, wherein a mixing amount of the organic acid may be more than 0% by weight and 10% or less by weight based on a total amount of a flux. [Concept 8] [0020] A liquid flux may comprise: the flux composition according to any one of Concepts 3 to 7; and a solvent. [Concept 9] [0021] A flux cored solder in which the flux composition according to any one of Concepts 3 to 7 may be filled. [Concept 10] [0022] A solder paste may comprise: the flux composition according to any one of Concepts 3 to 7; a thixotropic agent; a solvent; and solder powders. 3