Soldering iron

Solder melts at approximately 185 °C (365 °F). Soldering irons are designed to reach a temperature range of 200 to 480 °C (392 to 896 °F).

A variation is the Scope soldering iron, common in Australia, which operates from a low-voltage source such as transformer or battery, and heats in seconds when the user pushes the thumb-guard, which then acts as a heat controller.

Simple soldering irons reach a temperature determined by thermal equilibrium, dependent upon power input and cooling by the environment and the materials it comes into contact with. The iron temperature will drop when in contact with a large mass of metal such as a chassis; a small iron will lose too much temperature to solder a large connection. More advanced irons for use in electronics have a mechanism with a temperature sensor and method of temperature control to keep the tip temperature steady; more power is available if a connection is large. Temperature-controlled irons may be free-standing, or may comprise a head with heating element and tip, controlled by a base called a soldering station, with control circuitry and temperature adjustment and sometimes display.

For soldering and desoldering small surface-mount components with two terminals, such as some links, resistors, capacitors, and diodes, soldering tweezers can be used; they can be either free-standing or controlled from a soldering station. The tweezers have two heated tips mounted on arms whose separation can be manually varied by squeezing gently against spring force, like simple tweezers; the tips are applied to the two ends of the component. The main purpose of the soldering tweezers is to melt solder in the correct place; components are usually moved by simple tweezers or vacuum pickup.

Some tips have a heater and a thermocouple-based temperature sensor embedded to facilitate a more precise temperature control (TS100 and T12, for instance).

A wet small sponge, often supplied with soldering equipment, can be used to wipe the tip. For lead-free solder a slightly more aggressive cleaning, with brass shavings, can be used. Soldering flux will help to remove oxide; the more active the flux the better the cleaning, although acidic flux used on circuit boards that is not carefully cleaned off will cause corrosion. A tip which is cleaned but not retinned is susceptible to oxidation.

Soldering iron tips are made of a copper core plated various metals including iron. The copper is used for heat transfer and the other platings are for durability. Copper is very easily corroded, eating away the tip, particularly in lead-free work; iron is not. Cleaning tips requires the removal of oxide without damaging the iron plating and exposing the copper to rapid corrosion. The use of solder already containing a small amount of copper can slow corrosion of copper tips.

In cases of severe oxidation not removable by gentler methods, abrasion with something hard enough to remove oxide but not so hard as to scratch the iron plating can be used. A brass wire scourer, brush, or wheel on a bench grinder, can be used with care. Sandpaper and other tools may be used but are likely to damage the plating.

Temperature-controlled soldering irons with higher wattage (40W-60W) are better than low-wattage irons. It does not mean that temperature-controlled soldering irons with higher wattage apply more heat to the solder joint - it simply means that temperature-controlled soldering irons with higher wattage have more power available to heat the soldering joint if needed.