Provided is flux for resin flux cored solder using in a soldering method in which the resin flux cored solder is supplied into a through hole formed along a central axis of a soldering iron. The flux contains volatile rosin in an amount of 70 wt % or more and 98 wt % or less, non-volatile rosin in an amount of 0 wt % or more and 10% or less, and an activator in an amount of 2 wt % or more and 30 wt % or less, the activator including an organic acid in an amount of 0 wt % or more and 15 wt % or less, an organohalogen compound in an amount of 0.5 wt % and 15 wt % or less, an amine in an amount of 0 wt % or more and 5 wt % or less, and an amine hydrohalide salt in an amount of 0 wt % or more and 2.5 wt % or less.

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.

A solder composition contains: flux composition containing (A) rosin-based resin, (B) activator, and (C) solvent; and (D): solder powder with a melting point of 200 to 250 degrees C. The component (A) contains (A1) rosin-based resin with a softening point of 120 degrees C. or more and an acid number of 220 mgKOH/g or more and (A2) rosin-based resin with a softening point of 100 degrees C. or less and an acid number of 20 mgKOH/g or less. The component (C) contains (C1) hexanediol solvent with a melting point of 40 degrees C. or more and a boiling point of 220 degrees C. or less and (C2) solvent with a viscosity of 10 mPa.Math.s or less at 20 degrees C. and a boiling point of 270 degrees C. or more. A content of the component (A1) ranges from 15 to 25 mass % with respect to the flux composition (100 mass %).

Provided are a resin composition for soldering with not only improved wetting and spreading properties and but also excellent reliability and processability, a resin flux cored solder and a flux coated solder using this resin composition for soldering, and a liquid flux.

The resin composition for soldering includes 1 wt % or more and 40 wt % or less of: any of a dimer acid which is a reaction product of oleic acid and linoleic acid, a trimer acid which is a reaction product of oleic acid and linoleic acid, a hydrogenated dimer acid obtained by adding hydrogen to a dimer acid which is a reaction product of oleic acid and linoleic acid, or a hydrogenated trimer acid obtained by adding hydrogen to a trimer acid which is a reaction product of oleic acid and linoleic acid; or a total of two or more of a dimer acid which is a reaction product of oleic acid and linoleic acid, a trimer acid which is a reaction product of oleic acid and linoleic acid, a hydrogenated dimer acid obtained by adding hydrogen to a dimer acid which is a reaction product of oleic acid and linoleic acid, and a hydrogenated trimer acid obtained by adding hydrogen to a trimer acid which is a reaction product of oleic acid and linoleic acid, and 30 wt % or more and 99 wt % or less of a rosin.

It is an object of the present invention to provide flux and a solder material of which the activity hardly decreases even at a high temperature and which can also suppress the occurrence of migration. Flux containing an isocyanuric acid derivative containing two or more carboxyl groups and the like are provided.

An object of the present invention is to provide a flux which does not precipitate a crystal and can improve solder wettability. A flux comprising 0.4 to 10.0 mass % of ditolylguanidine and 1.0 to 10.0 mass % of an organic acid, and not comprising diphenylguanidine as an amine compound.

It is an object of the present invention to provide flux and a solder material of which the activity hardly decreases even at a high temperature and which can also suppress the occurrence of migration. Flux containing an isocyanuric acid derivative containing two or more carboxyl groups and the like are provided.

Provided is a flux activator containing a halogen compound represented by formula 1 below: ##STR00001## where X.sup.1 and X.sup.2 represent different halogen atoms, R.sup.1 and R.sup.2 are each a group represented by any one of formulas OH, OR.sup.3, OC(O)R.sup.4, and OC(O)NHR.sup.5, R.sup.1 and R.sup.2 optionally represent the same group or different groups, R.sup.3, R.sup.4, and R.sup.5 are each an aromatic hydrocarbon group having 1 to 18 carbon atoms or an aliphatic hydrocarbon group having 1 to 18 carbon atoms, and R.sup.3, R.sup.4, and R.sup.5 optionally represent the same group or different groups.

Provided is a flux containing not less than 11.0 degrees and not more than 17.0 of a contact angle between the flux and a resist substrate on which the flux has been printed to have 1.0 mm of a diameter and 0.15 mm of a thickness when heating the resist substrate at 150 degrees C. for 30 seconds and cooling the resist substrate to a room temperature. The flux also contains more than zero seconds and not more than 2.0 seconds of a zero-cross time when heating a Cu plate at 150 degrees C. in a thermostat oven for 12 hours, applying the flux onto the baked Cu plate, and dipping the baked Cu plate onto which the flux is applied into a Sn-3.0Ag-0.5Cu alloy at a dipping speed of 15 mm/sec and by 2.0 mm of a dipped depth.

Provided is a flux for resin-cored solder that is used in resin-cored solder that is supplied into a through hole formed along a central axis of a soldering iron. The flux includes 60% by mass to 99.9% by mass of a rosin ester to a total mass of the flux, 0.1% by mass to 15% by mass of a covalent halogen compound to the total mass of the flux, and more than 0% by mass to 10% by mass of rosin amine, N,N-diethyloctylamine, or rosin amine and N,N-diethyloctylamine to the total mass of the flux.