Soldering

soldering

Process that uses metal alloys with low melting points to join metallic surfaces without melting them. Tin-lead solders, once widely used in the electrical and plumbing industries, are now replaced by lead-free alloys. Such alloys are also used to solder brass and copper automobile radiators. Solders are supplied in wire, bar, or premixed-paste form, depending on the application. Soldering can be carried out using a torch, a soldering iron, a flame heater, or an induction heater. See also brazing, flux.

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Soldering

A low-temperature metallurgical joining method in which the solder (joining material) has a much lower melting point than the surfaces to be joined (substrates). Because of its lower melting point, solder can be melted and brought into contact with the substrates without melting them. During the soldering process, molten solder wets the substrate surfaces (spreads over them) and solidifies on cooling to form a solid joint.

The most important technological applications of solders are in the assembly of electronic devices, where they are used to make metallic joints between conducting wires, films, or contacts. They are also used for the routine low-temperature joining of copper plumbing fixtures and other devices. In addition, solder is used in the fusible joints of fire safety devices and other high-temperature detectors; the solder joint liquefies if the ambient temperature exceeds the solder's melting point, releasing a sprinkler head or triggering some other protective operation.

Tin or indium content is included in solder to facilitate bonding to the metals that are most commonly soldered, such as copper (Cu), nickel (Ni), and gold (Au). Tin and indium form stable intermetallic compounds with copper and nickel, and indium also forms intermetallics with gold. The intermetallic reaction at the solder-substrate interface creates a strong, stable bond. See Alloy, Intermetallic compounds