Soldering iron

A soldering iron is a hand tool used in soldering. It supplies heat to melt solder so that it can flow into the joint between two workpieces.

A soldering iron is composed of a heated metal tip and an insulated handle. Heating is often achieved electrically, by passing an electric current (supplied through an electrical cord or battery cables) through a resistive heating element. Cordless irons can be heated by combustion of gas stored in a small tank, often using a catalytic heater rather than a flame. Simple irons less commonly used than in the past were simply a large copper bit on a handle, heated in a flame.

Soldering irons are most often used for installation, repairs, and limited production work in electronics assembly. High-volume production lines use other soldering methods. Large irons may be used for soldering joints in sheet metal objects. Less common uses include pyrography (burning designs into wood) and plastic welding.

For electrical and electronics work, a low-power iron, a power rating between 15 and 35 watts, is used. Higher ratings are available, but do not run at higher temperature; instead there is more heat available for making soldered connections to things with large thermal capacity, for example, a metal chassis. Some irons are temperature-controlled, running at a fixed temperature in the same way as a soldering station, with higher power available for joints with large heat capacity. Simple irons run at an uncontrolled temperature determined by thermal equilibrium; when heating something large their temperature drops a little, possibly too much to melt solder.

Small irons heated by a battery, or by combustion of a gas such as butane in a small self-contained tank, can be used when electricity is unavailable or cordless operation is required. The operating temperature of these irons is not regulated directly; gas irons may change power by adjusting gas flow. Gas-powered irons may have interchangeable tips including different size soldering tips, hot knife for cutting plastics, miniature blow-torch with a hot flame, and small hot air blower for such applications as shrinking heat shrink tubing.

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