A lead-free solder alloy may comprise tin, silver, copper, bismuth, cobalt, titanium, and antimony. The alloy may further comprise antimony, nickel, or both. The silver may be present in an amount from about 3.1% to 3.8% by weight of the solder. The copper may be present in an amount from about 0.5% to 0.8% by weight of the solder. The bismuth may be present in an amount from about 0.0% (or 1.5%) to about 3.2% by weight of the solder. The cobalt may be present in an amount from about 0.03% to about 1.0% (or 0.05%) by weight of the solder. The titanium may be present in an amount from about 0.005% to about 0.02% by weight of the solder. The antimony may be present in an amount between about 1.0% to about 3.0% by weight of the solder. The balance of the solder is tin.

A flux containing 0.1 to 20 wt % of 2-hydroxyisobutyric acid as an activator, 10 to 60 wt % of a cationic surfactant and 5 to 60 wt % of a nonionic surfactant. A solder paste contains a flux containing 0.1 to 20 wt % of 2-hydroxyisobutyric acid as an activator, 10 to 60 wt % of a cationic surfactant, and 5 to 60 wt % of a nonionic surfactant and a metal powder.

A lead-free silver-free solder alloy may comprise tin, copper, bismuth, cobalt, and antimony. Alternatively, the alloy may comprise gallium in lieu of cobalt. The alloy may further comprise nickel, germanium, or both. The copper may be present in an amount from about 0.5% to 0.9% by weight of the solder. The bismuth may be present in an amount from about 1.0% to about 3.5% by weight of the solder. The cobalt may be present in an amount from about 0.02% to about 0.08% by weight of the solder. Where gallium is used in lieu of cobalt, the gallium may be present in an amount from about 0.2% to about 0.8% by weight of the solder. The antimony may be present in an amount between about 0.0% to about 0.09% by weight of the solder. The balance of the solder is tin.

A lead-free solder alloy includes 2.0% by mass or more and 4.0% by mass or less of Ag, 0.3% by mass or more and 0.7% by mass or less of Cu, 1.2% by mass or more and 2.0% by mass or less of Bi, 0.5% by mass or more and 2.1% by mass or less of In, 3.0% by mass or more and 4.0% by mass or less of Sb, 0.001% by mass or more and 0.05% by mass or less of Ni, 0.001% by mass or more and 0.01% by mass or less of Co, and the balance being Sn.

A method for manufacturing a heat exchanger (1) includes joining an inner fin (3) to a hollow structure (20) formed from at least two clad plates (200a, 200b) by heating and brazing a filler metal layer (B). Each clad plate has a core layer (A) composed of an aluminum alloy that contains Mg: 0.40-1.0 mass %. The filler metal layer is composed of an aluminum alloy that contains Si: 4.0-13.0 mass %, and further contains Li: 0.0040-0.10 mass %, Be: 0.0040-0.10 mass %, and/or Bi: 0.01-0.30 mass %. The inner fin is composed of an aluminum alloy that contains Si: 0.30-0.70 mass % and Mg: 0.35-0.80 mass %. A flux (F) that contains cesium (Cs) is applied along a contact part (201), and the vicinity thereof, of the at least two clad plates prior to the heating. A heat exchanger (1) may be manufactured according to this method.

A thermal treatment method for conditioning or restoring bismuth containing lead-free solder in a solder joint assembly. The method comprising heating the solder in the assembly to a temperature near the solvus.

Provided are: a resin composition for soldering use, which has excellent compatibility with a rosin-based resin and excellent temperature cycle reliability and is therefore suitable for a flux for soldering use; and a soldering composition and a flux cored solder, in each of which the resin composition for soldering use is used. The resin composition for soldering use comprises: an acrylic resin having a number average molecular weight of 500 or more and less than 2000 as determined by mass spectrometry using a time-of-flight mass spectrometer; and a rosin-based resin, a polyethylene-based resin or a polypropylene-based resin. Alternatively, the resin composition for soldering use comprises: an acrylic resin having a weight average molecular weight of 500 or more and less than 2000 as determined by mass spectrometry using a time-of-flight mass spectrometer; and a rosin-based resin, a polyethylene-based resin or a polypropylene-based resin.

Solder pastes comprise a high temperature solder powder, a low temperature solder powder and flux. The melting temperature of the low temperature solder powder is lower than that of the high temperature solder powder. The high temperature solder powder and the low temperature solder powder are both capable of wetting upon heating.

A method of making an amalgamation preform includes providing a particle-liquid mixture containing a plurality of types of solid particles and a liquid base metal. The plurality of types of solid particles at least includes reactive particles, reactable with the base metal, and non-reactive magnetic particles. A magnetic field is applied to the particle-liquid mixture to magnetically disperse the plurality of types of solid particles in the liquid base metal to form a particle-liquid dispersion without substantially inducing a reaction between the reactive particles and the liquid base metal. A playdough-like amalgamation preform is prepared based on the particle-liquid dispersion without solidifying the liquid base metal.

A method of using an amalgamation preform includes providing mating bonding surfaces and placing a particle-liquid mixture corresponding to the amalgamation preform between the mating bonding surfaces. The particle-liquid mixture contains a plurality of types of solid particles and a base metal in a liquid form, and the plurality of types of solid particles at least includes reactive particles reactable with the base metal and non-reactive magnetic particles. A first magnetic field is applied to the particle-liquid mixture to magnetically disperse the plurality of types of solid particles in the liquid base metal to form a particle-liquid dispersion; and a second magnetic field is applied to cure the particle-liquid dispersion to allow reactions between the reactive particles and the base metal.