The present disclosure provides a copper-phosphorus-tin brazing wire and a preparation method thereof, relates to the technical field of brazing materials. The copper-phosphorus-tin brazing wire is of a three-layer structure, the inner layer is Cu, the middle layer is Cu-14P alloy, and the outer layer is Sn, wherein the mass percentage of Sn is over 7%. The present disclosure solves the technical problems in the prior art that the copper-phosphorus-silver brazing filler metal is prone to produce defects such as pores and inclusions when brazing copper alloys, which leads to the decline of the mechanical properties of the joint, and simultaneously provides the preparation method of the copper-phosphorus-tin brazing wire, such that the technical problem that it is difficult to obtain copper-phosphorus-tin brazing wire with a wire diameter below 0.5 mm under the condition of high Sn content is solved.

The invention concerns a flux for brazing, a process for brazing metal parts employing said flux, a flux composition containing said flux, aluminum parts coated with said flux or said flux composition, a process for brazing and a brazed metal object obtainable by said brazing process. The flux is high in KAlF.sub.4 and low in K.sub.3AlF.sub.6.

The invention concerns a flux for brazing, a process for brazing metal parts employing said flux, a flux composition containing said flux, aluminum parts coated with said flux or said flux composition, a process for brazing and a brazed metal object obtainable by said brazing process. The flux is high in KAlF.sub.4 and low in K.sub.3AlF.sub.6.

According to an aspect of the present invention, there is provided a flux-cored wire including a steel sheath and a flux that fills the steel sheath. The flux contains fluorides of which a total value of F-equivalent values is 0.21% or more, oxides of which the total value of amounts ranges from 0.30% to 3.50%, and carbonates of which a total value of amounts ranges from 0% to 3.50%. An amount of CaO ranges from 0% to 0.20%. An amount of iron powder ranges from 0% to less than 10.0%. A Y-value is 5.0% or less. The amount of CaF.sub.2 is less than 0.50%. The amount of Ti oxides ranges from 0.10% to 2.50%. A ratio of to ranges from 0.10 to 4.00. A total value of amounts of MgCO.sub.3, Na.sub.2CO.sub.3, and LiCO.sub.3 ranges from 0% to 3.00%. A chemical composition excluding the fluorides, the oxides, the CaO, the carbonates, and the iron powder is within a predetermined range. Ceq ranges from 0.10% to 0.44%.

According to an aspect of the present invention, there is provided a flux-cored wire including a steel sheath and a flux that fills the steel sheath. The flux contains fluorides of which a total value of F-equivalent values is 0.21% or more, oxides of which the total value of amounts ranges from 0.30% to 3.50%, and carbonates of which a total value of amounts ranges from 0% to 3.50%. An amount of CaO ranges from 0% to 0.20%. An amount of iron powder ranges from 0% to less than 10.0%. A Y-value is 5.0% or less. The amount of CaF.sub.2 is less than 0.50%. The amount of Ti oxides ranges from 0.10% to 2.50%. A ratio of to ranges from 0.10 to 4.00. A total value of amounts of MgCO.sub.3, Na.sub.2CO.sub.3, and LiCO.sub.3 ranges from 0% to 3.00%. A chemical composition excluding the fluorides, the oxides, the CaO, the carbonates, and the iron powder is within a predetermined range. Ceq ranges from 0.10% to 0.44%.

Provided are flux in which solder wettability is improved, and a solder paste in which the flux is used. The flux contains 0.5-20.0 wt % of a (2-carboxyalkyl)isocyanurate adduct, and 5.0-45.0 wt % of a rosin, and furthermore contains a solvent. The (2-carboxyalkyl)isocyanurate adduct is a mono(2-carboxyalkyl)isocyanurate adduct, a bis(2-carboxyalkyl)isocyanurate adduct, a tris(2-carboxyalkyl)isocyanurate adduct, or a combination of two or more of these.

Provided is a flux capable of obtaining predetermined rheological characteristics both at room temperature and under a thermal history that is assumed for soldering and capable of suppressing the amount of a residue after soldering to realize a low residue. The flux contains a first alcohol compound that has two or more OH groups and has a melting point of lower than 25 C. and a second alcohol compound that has two or more OH groups and has a melting point of higher than 25 C., the first alcohol compound is glycerin, the second alcohol compound is 2,5-dimethylhexane-2,5-diol, the flux has a viscosity of 10 Pa.Math.s or more and 50 Pa.Math.s or less at 25 C. and has a viscosity of more than 0 Pa.Math.s and 1 Pa.Math.s or less at 100 C., and, in a case where 10 mg of the flux is heated up to 25 C. to 250 C. under a N.sub.2 atmosphere at a temperature rise rate of 10 C./min, the weight of the flux after heating is 15% or less of the weight of the flux before heating.

A flux according to the present invention contains a rosin methyl ester in which the flux is a solid or solid-like flux at 25 C., and is used for an inside of a flux-cored solder or an exterior of a flux-coated solder.

A flux according to the present invention contains a rosin methyl ester in which the flux is a solid or solid-like flux at 25 C., and is used for an inside of a flux-cored solder or an exterior of a flux-coated solder.

The present invention accurately distinguishes a soldering material less likely to oxidize. A Cu core ball has a Cu ball having a predetermined size, and a solder layer coating the Cu ball. The Cu ball provides a space between a semiconductor package and a printed circuit board. The Cu core ball has the soldering material having lightness greater than or equal to 62.5 in L*a*b* color space subsequent to a heating storage test performed for 72 hours in a temperature-controlled bath at 150 C. with a temperature of 25 C. and 40% humidity, and the soldering material, prior to the heating storage test, having lightness greater than or equal to 65 in the L*a*b* color space and yellowness less than or equal to 7.0 in the L*a*b* color space.