Abstract: A soldering flux of the present invention contains, as a base resin, an acrylic resin (A) having an acid value of 0 to 70, and an acrylic resin (B) having an acid value of 30 to 230. The acrylic resin (A) is obtained by polymerization of a monomer mixture containing alkyl (meth)acrylate having an alkyl group having carbon atoms of 12 to 23. The acrylic resin (B) is obtained by polymerization of a monomer mixture containing alkyl (meth)acrylate having an alkyl group having carbon atoms of 6 to 10. The acid value of the acrylic resin (B) is higher than the acid value of the acrylic resin (A), and a difference between these two resins is 15 or more.

Abstract: A soldering flux of the present invention contains, as a base resin, an acrylic resin (A) having an acid value of 0 to 70, and an acrylic resin (B) having an acid value of 30 to 230. The acrylic resin (A) is obtained by polymerization of a monomer mixture containing alkyl(meth)acrylate having an alkyl group having carbon atoms of 12 to 23. The acrylic resin (B) is obtained by polymerization of a monomer mixture containing alkyl(meth)acrylate having an alkyl group having carbon atoms of 6 to 10. The acid value of the acrylic resin (B) is higher than the acid value of the acrylic resin (A), and a difference between these two resins is 15 or more.

Abstract: A soldering flux of the present invention contains, as a base resin, an acrylic resin (A) having an acid value of 0 to 70, and an acrylic resin (B) having an acid value of 30 to 230. The acrylic resin (A) is obtained by polymerization of a monomer mixture containing alkyl(meth)acrylate having an alkyl group having carbon atoms of 12 to 23. The acrylic resin (B) is obtained by polymerization of a monomer mixture containing alkyl(meth)acrylate having an alkyl group having carbon atoms of 6 to 10. The acid value of the acrylic resin (B) is higher than the acid value of the acrylic resin (A), and a difference between these two resins is 15 or more.

Abstract: A reflow soldering system wherein a heating oven is provided with a contact heating unit which has a transport rail and a top heat transfer heater, and with a hot gas blowing heating unit, the transport rail and top heat transfer heater are respectively provided with heaters which heat the outer edge part of the printed circuit board, and the transport rail or top heat transfer heater moves in an up-down direction so that the transport rail and top heat transfer heater clamp and heat the outer edge part of the printed circuit board.

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.

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.