A magnetic-field melting solder that melts by the action of an AC magnetic field is provided. The magnetic-field melting solder includes solder material; and magnetic material composing of ferrite or Ni, a proportion of the magnetic material to the entire magnetic-field melting solder being 0.005% to 5% by weight. A joining method using the magnetic-field melting solder includes providing the magnetic-field melting solder between an electrode on a substrate and an electrode of an electronic component, and joining together the electrode on the substrate and the electrode of the electronic component by generating an AC magnetic field around the substrate and thereby melting the magnetic-field melting solder.

A flux containing: a rosin; a solvent (S); a thixotropic agent; and an activator is disclosed. The rosin contains a rosin amine. The solvent (S) contains a first solvent (S1) having a boiling point of 250° C. or less, and the amount of the first solvent (S1) relative to the total amount of the solvent (S) is 50% by mass or more and 100% by mass or less.

A flux containing: a rosin; a solvent (S); a thixotropic agent; and an activator is disclosed. The rosin contains a rosin amine. The solvent (S) contains a first solvent (S1) having a boiling point of 250° C. or less, and the amount of the first solvent (S1) relative to the total amount of the solvent (S) is 50% by mass or more and 100% by mass or less.

A flux-cored wire of the present disclosure has a steel sheath and a flux filled at an inside of the steel sheath, has a total amount of moisture by ratio with respect to a total wire mass of 300 ppm or less, has flux containing fluorides, and has an amount of the fluorides by ratio with respect to the total wire mass of, by total of values converted to F, 0.11 mass % or more and 2.50 mass % or less. If using the flux-cored wire of the present disclosure for welding, a stable weld shape can be obtained and, further, the amount of diffusible hydrogen of the weld metal can be reduced. For this reason, the flux-cored wire of the present disclosure can be suitably used for welding high strength steel such as ferrite steel.

An iodine-containing cyclic compound including no carboxy group and including one ring skeleton or a plurality of ring skeletons forming a fused ring in one molecule, is provided. The ring of the ring skeleton includes only a carbon atom, or a carbon atom, and a nitrogen atom and/or an oxygen atom, and an iodine atom is bonded to at least one of the atoms constituting the ring of the ring skeleton.

An iodine-containing cyclic compound including no carboxy group and including one ring skeleton or a plurality of ring skeletons forming a fused ring in one molecule, is provided. The ring of the ring skeleton includes only a carbon atom, or a carbon atom, and a nitrogen atom and/or an oxygen atom, and an iodine atom is bonded to at least one of the atoms constituting the ring of the ring skeleton.

Provided is a flux that allows soldering to be performed without requiring a step of removing a Cu-OSP film even with a Cu-OSP processed substrate. This flux containing rosin, an organic acid, a benzimidazole-based compound, and a solvent is characterized in that 30% by mass or more and 70% by mass or less of the rosin, 1% by mass or more and 10% by mass or less of the organic acid, 0.2% by mass or more and 10% by mass or less of the benzimidazole-based compound, and 20% by mass or more and 60% by mass or less of the solvent, wherein the benzimidazole-based compound is composed of at least one of 2-alkylbenzimidazole and a salt of 2-alkylbenzimidazole hydrohalide.

Provided is a flux that allows soldering to be performed without requiring a step of removing a Cu-OSP film even with a Cu-OSP processed substrate. This flux containing rosin, an organic acid, a benzimidazole-based compound, and a solvent is characterized in that 30% by mass or more and 70% by mass or less of the rosin, 1% by mass or more and 10% by mass or less of the organic acid, 0.2% by mass or more and 10% by mass or less of the benzimidazole-based compound, and 20% by mass or more and 60% by mass or less of the solvent, wherein the benzimidazole-based compound is composed of at least one of 2-alkylbenzimidazole and a salt of 2-alkylbenzimidazole hydrohalide.

If a flux contains an amount of thixotropic agent necessary for obtaining the effect of suppressing a heating sagging, the amount of flux residue increases, and, if applied for uses that do not involve washing, a large amount of flux residue derived from the thixotropic agent remains around the soldered portions, thereby affecting chemical and electrical reliability; and that washing performance is poor in uses involving washing of the flux residue. Accordingly, this soldering flux contains nanofibers of one or more kinds from among polysaccharides, modified polysaccharides, and incompletely modified polysaccharides being modified from polysaccharides into modified polysaccharides, by an amount of 50 wt ppm or more and 3000 wt ppm or less with respect to a total amount of flux.

If a flux contains an amount of thixotropic agent necessary for obtaining the effect of suppressing a heating sagging, the amount of flux residue increases, and, if applied for uses that do not involve washing, a large amount of flux residue derived from the thixotropic agent remains around the soldered portions, thereby affecting chemical and electrical reliability; and that washing performance is poor in uses involving washing of the flux residue. Accordingly, this soldering flux contains nanofibers of one or more kinds from among polysaccharides, modified polysaccharides, and incompletely modified polysaccharides being modified from polysaccharides into modified polysaccharides, by an amount of 50 wt ppm or more and 3000 wt ppm or less with respect to a total amount of flux.