A solder paste includes a solder powder and a flux. The flux includes a rosin, an activator, a solvent, and a thixotropic agent containing a polyethylene glycol. A content of the polyethylene glycol is 10 mass % to 20 mass % with respect to a total mass of the flux, a content of the thixotropic agent excluding the polyethylene glycol is 5 mass % or less with respect to the total mass of the flux, and a content of the rosin is more than 15 mass % and 50 mass % or less with respect to the total mass of the flux.

A TIG welding flux for chromium-molybdenum steel is used to form a weld bead with high mechanical strength and high fracture toughness between two chromium-molybdenum steel workpieces. The TIG welding flux for chromium-molybdenum steel includes 30-44 wt % of silicon dioxide (SiO.sub.2), 20-35 wt % of manganese(IV) oxide (MnO.sub.2), 14-24 wt % of chromium(III) oxide (Cr.sub.2O.sub.3), 9-19 wt % of nickel(III) oxide (Ni.sub.2O.sub.3), 7-14 wt % of molybdenum trioxide (MoO.sub.3) and 5-10 wt % of calcium fluoride (CaF.sub.2).

A TIG welding flux for chromium-molybdenum steel is used to form a weld bead with high mechanical strength and high fracture toughness between two chromium-molybdenum steel workpieces. The TIG welding flux for chromium-molybdenum steel includes 30-44 wt % of silicon dioxide (SiO.sub.2), 20-35 wt % of manganese(IV) oxide (MnO.sub.2), 14-24 wt % of chromium(III) oxide (Cr.sub.2O.sub.3), 9-19 wt % of nickel(III) oxide (Ni.sub.2O.sub.3), 7-14 wt % of molybdenum trioxide (MoO.sub.3) and 5-10 wt % of calcium fluoride (CaF.sub.2).

Compositions and methods for coupling metals to aluminum surfaces are provided. The compositions are prepared as aqueous solutions or suspensions, and can be applied to the aluminum surface using conventional printing techniques. Rheology of the printable composition can be adjusted to provide a gel or a cream. Curing steps, if necessary, are performed at low temperatures that are compatible with plastic/polymer components of mass produced devices, such as aluminum RFID antennae.

Compositions and methods for coupling metals to aluminum surfaces are provided. The compositions are prepared as aqueous solutions or suspensions, and can be applied to the aluminum surface using conventional printing techniques. Rheology of the printable composition can be adjusted to provide a gel or a cream. Curing steps, if necessary, are performed at low temperatures that are compatible with plastic/polymer components of mass produced devices, such as aluminum RFID antennae.

Provided is a solder paste which uses a conventional flux, and for which long-term preservation is made possible and an easy preservation method can be realized by suppressing changes in the viscosity of the paste over time. This solder paste is provided with a solder powder, a zirconium oxide powder, and a flux, and changes in the viscosity of the paste over time are suppressed.

Provided is a solder paste which uses a conventional flux, and for which long-term preservation is made possible and an easy preservation method can be realized by suppressing changes in the viscosity of the paste over time. This solder paste is provided with a solder powder, a zirconium oxide powder, and a flux, and changes in the viscosity of the paste over time are suppressed.

A flux for a solder paste includes rosin, an activator and a solvent. The solvent includes a monoalkylene glycol-based solvent and a solid solvent that is solid at 20° C. The total content of the monoalkylene glycol-based solvent and the solid solvent ranges from 40% by mass to 60% by mass with the total amount of the flux as 100%. The content of the solid solvent ranges from 5% by mass to 25% by mass with the total amount of the flux as 100%.

A flux for a solder paste includes rosin, an activator and a solvent. The solvent includes a monoalkylene glycol-based solvent and a solid solvent that is solid at 20° C. The total content of the monoalkylene glycol-based solvent and the solid solvent ranges from 40% by mass to 60% by mass with the total amount of the flux as 100%. The content of the solid solvent ranges from 5% by mass to 25% by mass with the total amount of the flux as 100%.

Provided are a solder alloy and a solder joint which have high tensile strength, can suppress Ni leaching and can suppress generation of voids at a bonded interface. The solder alloy has an alloy composition consisting of, by mass %, Ag: 1.0 to 4.0%, Cu: 0.1 to 1.0%, Ni: 0.005 to 0.3%, Co: 0.003 to 0.1%, and Ge: 0.001 to 0.015% with the balance being Sn The alloy composition satisfies the following relation (1):

0.00030<(Ni/Co)×(1/Ag)×Ge<0.05   (1) Co, Ag, and Ge in the relation (1) each represent the contents (mass %) in the alloy composition.