Provided is a method for manufacturing high purity tin including: depositing electrodeposited tin on the surface of a cathode by electrowinning in an electrolytic bath in which a diaphragm is placed between an anode and the cathode, by using a raw material for tin as the anode and a leachate obtained by electrolytically leaching the raw material for tin in a sulfuric acid solution as an electrolytic solution, the electrolytic solution containing a smoothing agent for improving a surface property of the electrodeposited tin; discharging the electrolytic solution from the electrolytic bath such that lead in the discharged electrolytic solution is removed; and putting the electrolytic solution from which lead is removed back into the electrolytic bath.

Provided is a method for manufacturing high purity tin including: depositing electrodeposited tin on the surface of a cathode by electrowinning in an electrolytic bath in which a diaphragm is placed between an anode and the cathode, by using a raw material for tin as the anode and a leachate obtained by electrolytically leaching the raw material for tin in a sulfuric acid solution as an electrolytic solution, the electrolytic solution containing a smoothing agent for improving a surface property of the electrodeposited tin; discharging the electrolytic solution from the electrolytic bath such that lead in the discharged electrolytic solution is removed; and putting the electrolytic solution from which lead is removed back into the electrolytic bath.

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.

Provided are a solder alloy which has excellent temperature cycle characteristics and in which yellowish discoloration is suppressed, excellent wettability is maintained, and an increase in viscosity of a solder paste over time can be suppressed, and a solder paste, a solder ball, and a solder joint in which the solder alloy is used. The solder alloy consists of, by mass %, 1.0% to 5.0% of Ag, 0.5% to 3.0% of Cu, 0.5% to 7.0% of Sb, 0.0040% to 0.025% of As, and a balance of Sn.

Provided are a solder alloy which has excellent temperature cycle characteristics and in which yellowish discoloration is suppressed, excellent wettability is maintained, and an increase in viscosity of a solder paste over time can be suppressed, and a solder paste, a solder ball, and a solder joint in which the solder alloy is used. The solder alloy consists of, by mass %, 1.0% to 5.0% of Ag, 0.5% to 3.0% of Cu, 0.5% to 7.0% of Sb, 0.0040% to 0.025% of As, and a balance of Sn.

Any metal having a low α-ray emission, the metal being any one of tin, silver, copper, zinc, or indium, wherein an emission of an α-ray after heating the metal at 100° C. in an atmosphere for six hours is 0.002 cph/cm.sup.2 or less. Any metal of tin, silver, copper, zinc and indium each including lead as an impurity is dissolved to prepare a hydrosulfate aqueous solution of the metal and lead sulfate is precipitated and removed in the solution. The lead sulfate is precipitated in the hydrosulfate aqueous solution by adding a lead nitrate aqueous solution including lead having an α-ray emission of 10 cph/cm.sup.2 or less to the hydrosulfate aqueous solution, from which the lead sulfate has been removed, and, at the same time, the solution is circulated while removing the lead sulfate to electrowinning the metal using the hydrosulfate aqueous solution as an electrolytic solution.

Any metal having a low α-ray emission, the metal being any one of tin, silver, copper, zinc, or indium, wherein an emission of an α-ray after heating the metal at 100° C. in an atmosphere for six hours is 0.002 cph/cm.sup.2 or less. Any metal of tin, silver, copper, zinc and indium each including lead as an impurity is dissolved to prepare a hydrosulfate aqueous solution of the metal and lead sulfate is precipitated and removed in the solution. The lead sulfate is precipitated in the hydrosulfate aqueous solution by adding a lead nitrate aqueous solution including lead having an α-ray emission of 10 cph/cm.sup.2 or less to the hydrosulfate aqueous solution, from which the lead sulfate has been removed, and, at the same time, the solution is circulated while removing the lead sulfate to electrowinning the metal using the hydrosulfate aqueous solution as an electrolytic solution.

A flux according to the present invention is a flux for soldering, the flux including: an unsaturated aliphatic alcohol having one unsaturated bond, a thixotropic agent, and a solvent, in which the unsaturated aliphatic alcohol includes oleyl alcohol, and a content of the oleyl alcohol is 2.0 mass % or more and 12.0 mass % or less based on the entire flux.

A flux according to the present invention is a flux for soldering, the flux including: an unsaturated aliphatic alcohol having one unsaturated bond, a thixotropic agent, and a solvent, in which the unsaturated aliphatic alcohol includes oleyl alcohol, and a content of the oleyl alcohol is 2.0 mass % or more and 12.0 mass % or less based on the entire flux.

A solder alloy is used for soldering, and its chemical composition in mass % includes: 2.0 to 4.0% of Ag; 0.6 to 1.2% of Cu; 2.0 to 5.0% of Sb; 1.1 to 3.5% of In; 0 to 0.20% of Ni; 0 to 0.20% of Co; 0 to 0.05% of Ge; and balance of Sn, and impurities.