Abstract: Provided is a solder alloy that contains 0.01 mass % or more and 0.1 mass % or less of Fe, 0.005 mass % or more and less than 0.02 mass % of Co, 0.1 mass % or more and 4.5 mass % or less of Ag, 0.1 mass % or more and 0.8 mass % or less of Cu, and the balance being Sn.

Abstract: Provided is a flux activator containing a halogen compound represented by formula 1 below: where X1 and X2 represent different halogen atoms, R1 and R2 are each a group represented by any one of formulas —OH, —O—R3, —O—C(?O)—R4, and —O—C(?O)—NH—R5, R1 and R2 optionally represent the same group or different groups, R3, R4, and R5 are each an aromatic hydrocarbon group having 1 to 18 carbon atoms or an aliphatic hydrocarbon group having 1 to 18 carbon atoms, and R3, R4, and R5 optionally represent the same group or different groups.

Abstract: Provided is a solder alloy that contains 0.01 mass % or more and 0.1 mass % or less of Fe, 0.005 mass % or more and less than 0.02 mass % of Co, 0.1 mass % or more and 4.5 mass % or less of Ag, 0.1 mass % or more and 0.8 mass % or less of Cu, and the balance being Sn.

Abstract: Provided is a flux activator containing a halogen compound represented by formula 1 below: where X1 and X2 represent different halogen atoms, R1 and R2 are each a group represented by any one of formulas —OH, —O—R3, —O—C(?O)—R4, and —O—C(?O)—NH—R5, R1 and R2 optionally represent the same group or different groups, R3, R4, and R5 are each an aromatic hydrocarbon group having 1 to 18 carbon atoms or an aliphatic hydrocarbon group having 1 to 18 carbon atoms, and R3, R4, and R5 optionally represent the same group or different groups.

Abstract: A solder paste according to an aspect of the invention includes, within a flux, an activator that has a dibasic acid with a molecular weight of 250 or less, a monobasic acid with a molecular weight of 150 or greater and 300 or less, and a dibasic acid with a molecular weight of 300 or greater and 600 or less; and at least one resin additive selected from the group consisting of high-density polyethylenes and polypropylenes. The solder paste has the resin additive in an amount of 4% by weight or greater and 12% by weight or less when the total amount of the flux is taken as 100% by weight, and has a viscosity of 400 Pa·s or greater at 80° C.

Abstract: A flux for a solder paste according to an aspect of the invention includes an acrylic resin obtained by radically copolymerizing a (meth)acrylate having a C6-C15 alkyl group and a (meth)acrylate other than the above-mentioned (meth)acrylate; and rosins. The weight ratio of the acrylic resin is 0.5 or greater and 1.2 or less when the weight of the rosins is taken as 1, and the flux for a solder paste is fluidized by application of a shear force of 10 Pa or greater and 150 Pa or less.