A flux containing an organic acid, a water-soluble base agent, and a solvent, but not containing water is adopted. In this flux, the organic acid includes 1,2,3-propanetricarboxylic acid. The water-soluble base agent is one or more selected from the group consisting of a nonionic surfactant and a weak cationic surfactant. The content of the 1,2,3-propanetricarboxylic acid is 1% by mass or more and 15% by mass or less with respect to the total amount of the entire flux, the total content of the water-soluble base agent is 30% by mass or more and 65% by mass or less with respect to the total amount of the entire flux, and the total content of the solvent is 30% by mass or more and 65% by mass or less with respect to the total amount of the entire flux. According to this flux, the wettability of solder can be enhanced and ball missing after reflow and flux residue washing is suppressed.

Undercooled liquid metallic core-shell particles, whose core is stable against solidification at ambient conditions, i.e. under near ambient temperature and pressure conditions, are used to join or repair metallic non-particulate components. The undercooled-shell particles in the form of nano-size or micro-size particles comprise an undercooled stable liquid metallic core encapsulated inside an outer shell, which can comprise an oxide or other stabilizer shell typically formed in-situ on the undercooled liquid metallic core. The shell is ruptured to release the liquid phase core material to join or repair a component(s).

Provided is a flux for solder paste including an organic component as a main component, which is composed of a fatty acid and an aliphatic primary amine.

Undercooled liquid metallic core-shell particles, whose core is stable against solidification at ambient conditions, i.e. under near ambient temperature and pressure conditions, are used to join or repair metallic non-particulate components. The undercooled-shell particles in the form of nano-size or micro-size particles comprise an undercooled stable liquid metallic core encapsulated inside an outer shell, which can comprise an oxide or other stabilizer shell typically formed in-situ on the undercooled liquid metallic core. The shell is ruptured to release the liquid phase core material to join or repair a component(s).

Provided are a flux, resin flux cored solder and a flux coated pellet which are washable with water. Resin flux cored solder is composed of solder having a linear shape and a flux filled in a substantially central part (core) of the cross section of the solder. The flux contains an amine for salt formation and an organic acid for salt formation, in which the amount of the organic acid is within a range between 10 parts by mass or more and 645 parts by mass or less based on 100 parts by mass of the amine. The organic acid for salt formation is composed of at least one organic acid selected from the group consisting of malonic acid, succinic acid, glutaric acid, tartaric acid, malic acid, diglycolic acid, and citric acid.

A solder alloy is provided which can withstand the severe characteristics of a temperature cycle between a low temperature of −40° C. and a high temperature of 125° C., withstand an external force applied due to, for example, riding on a curb or collision with a vehicle ahead for a long period of time, and can suppress change in viscosity of a solder paste over time. In addition, a solder paste, a solder ball, and a solder preform in which the solder alloy is used; a solder joint formed through the use thereof; and an on-board electronic circuit, an ECU electronic circuit, an on-board electronic circuit device, and an ECU electronic circuit device which include this solder joint are provided. The solder alloy contains, by mass %, 1% to 4% of Ag, 0.5% to 1.0% of Cu, 1.5% to 5.5% of Bi, 1.0% to 5.3% of Sb (or greater than 5.5% and less than or equal to 7.0% of Bi and 2.0% to 5.3% of Sb), 0.01% to 0.2% of Ni, 0.0040% to 0.0250% of As, and a balance of Sn.

Undercooled liquid metallic core-shell particles, whose core is stable against solidification at ambient conditions, i.e. under near ambient temperature and pressure conditions, are used to join or repair metallic non-particulate components. The undercooled-shell particles in the form of nano-size or micro-size particles comprise an undercooled stable liquid metallic core encapsulated inside an outer shell, which can comprise an oxide or other stabilizer shell typically formed in-situ on the undercooled liquid metallic core. The shell is ruptured to release the liquid phase core material to join or repair a component(s).

A resin composition for soldiering is provided. The resin composition includes 1 wt % or more and 40 wt % or less of a dimer acid, a trimer acid, or a combination thereof, 30 wt % or more and 99 wt % or less of a rosin, and 0 wt % or more and 13 wt % or less of a solvent. The dimer acid is selected from a dimer acid that is a reaction product of oleic acid and linoleic acid, a hydrogenated dimer acid obtained by adding hydrogen to a dimer acid that is a reaction product of oleic acid and linoleic acid, and a combination thereof. The trimer acid is selected from a trimer acid that is a reaction product of oleic acid and linoleic acid, a hydrogenated trimer acid obtained by adding hydrogen to a trimer acid that is a reaction product of oleic acid and linoleic acid, and a combination thereof.

A solder paste contains a flux and a metal powder, wherein the flux contains: 0.5% by mass to 20.0% by mass of a (carboxyalkyl)isocyanurate adduct; 5.0% by mass to 45.0% by mass of a rosin; and a solvent. The (carboxyalkyl)isocyanurate adduct is at least one selected from the group consisting of mono(carboxyalkyl)isocyanurate adducts, bis(carboxyalkyl)isocyanurate adducts and tris(carboxyalkyl)isocyanurate adducts.

A solder composition of the invention contains: a flux composition containing (A) a rosin resin, (B) an activator, (C) an imidazoline compound having a phenyl group, and (D) an antioxidant; and (E) solder powder, in which the (B) component contains (B1) an organic acid, the (B1) component contains at least one selected from the group consisting of (B11) 1-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, and 1,4-dihydroxy-2-naphthoic acid, and the (C) component is at least one selected from the group consisting of 2-phenylimidazoline and 2-benzylimidazoline.