The metal or alloy used as a filler metal in soldering, which has a liquidus not exceeding 450°C (840°F) and below the solidus of the base metal. Solders are generally referred to as being “hard” or “soft.” These terms do indicate relative hardness (or strength), but more generally indicate relative melting points; with the hard solders melting at higher temperatures, often above 450°C (840°F), thereby making them actually braze fillers.

Solders are based on low-melting metals such as lead, cadmium, bismuth, zinc, indium or tin, and their low-melting (virtually always eutectic) alloys. See SOLDERING.

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