A soldering iron is a heated hand tool used to join two metal surfaces together by melting a filler metal (called solder) between them. It’s the go-to tool for electronics work, from assembling circuit boards to repairing broken wires, but it also shows up in plumbing, jewelry making, stained glass, and general home repair. The iron itself doesn’t melt the workpieces. Instead, it melts the solder, which flows into the joint, cools, and forms a permanent electrical and mechanical bond.
How a Soldering Iron Works
The basic idea is simple: the iron’s tip heats up to a temperature that melts solder but not the parts you’re joining. Solder is a metal alloy, traditionally a mix of tin and lead, though lead-free versions are now common. Leaded solder melts at around 363°F, while lead-free solder requires higher temperatures, closer to 425°F. Most soldering irons operate well above those thresholds, often set to 650°F or 700°F, to ensure the solder flows quickly and cleanly.
When you touch the iron to a joint, the heat transfers through the metal surfaces. The solder melts on contact, flows into the gap between the two pieces, and wicks into place. A chemical cleaning agent called flux, usually built into the core of the solder wire, plays a critical role here. Flux breaks down the thin layer of oxidation that forms instantly on heated metal. Without it, the solder can’t properly “wet” the surface, and you end up with a weak, unreliable connection. By removing that oxide barrier and shielding the joint from oxygen in the air, flux lets the solder spread evenly and bond tightly.
Electronics and Circuit Board Assembly
This is the most common use for a soldering iron. In electronics, soldering creates the electrical connections between components and the copper traces on a printed circuit board (PCB). Every resistor, capacitor, microchip, and connector on a circuit board is held in place and electrically connected by a tiny blob of solder. For hobbyists building their own projects, repair technicians replacing a blown component, or factory workers assembling production boards, the soldering iron is the central tool.
PCB work typically calls for an iron with adjustable temperature control in the 25W to 60W range. That level of precision matters because too much heat can damage sensitive components or lift the copper pads right off the board. Too little heat produces “cold” joints that look dull and grainy and fail over time. A soldering iron also works in reverse for electronics: you can use it with a desoldering pump or desoldering wick to remove old solder, freeing a component for replacement. This rework process is essential for diagnosing faulty boards and swapping out damaged parts.
Home and Appliance Repair
Beyond building new electronics, soldering irons are a staple in everyday repair work. A broken wire inside a lamp, a loose connection on a speaker terminal, a cracked solder joint on an old appliance’s control board: these are all quick fixes with a soldering iron. Repair technicians use them to disassemble and replace damaged components, resolder connections that have come loose from vibration or heat cycling, and restore equipment to working condition without replacing entire assemblies.
If you’ve ever opened up a device and seen a wire dangling free or a component that’s clearly come unattached from its circuit board, a soldering iron is how you put it back. The skill ceiling is low for basic repairs. With a little practice, most people can make clean, reliable joints on household wiring and simple electronics.
Stained Glass, Jewelry, and Metalwork
Soldering irons aren’t limited to electronics. In stained glass work, artists wrap each piece of cut glass in thin copper foil, then use a soldering iron to melt solder along every seam, joining the pieces into a single panel. This requires a higher-wattage iron than delicate circuit board work, since you’re heating larger metal surfaces and need the solder to flow along longer seams. Jewelry makers use soldering irons (or small torches, depending on the metals involved) to join findings, clasps, and decorative elements. The principle is the same: melt a filler metal to bond two pieces without melting the pieces themselves.
Soldering Irons vs. Soldering Guns
You’ll sometimes see soldering guns alongside soldering irons at the hardware store, and they serve different purposes. A soldering gun is a bulkier, higher-wattage tool, typically 100W to 230W, designed for heavy work like joining thick stranded wire or soldering large metal connectors. The gun shape makes it easy to grip for quick, high-heat jobs, but the large tip and high output make it completely impractical for circuit board work.
For any through-hole or surface-mount electronics, you want a pencil-style soldering iron, ideally one that’s part of a temperature-controlled station. These stations have lighter, slimmer handles that let you maneuver between tiny components with much more control. A cheap plug-in iron will work for basic tasks, but a temperature-controlled station gives you consistent, repeatable results and protects sensitive parts from overheating.
Choosing the Right Tip
The shape of the soldering iron’s tip determines what kind of work it does well. Most irons let you swap tips easily, so you can match the tip to the job.
- Chisel tip: The most versatile and widely used shape. Its flat surface provides excellent heat transfer, making it ideal for general electronics, through-hole components, and connectors. If you only own one tip, make it a medium chisel.
- Conical tip: A fine point for precision work. Best for fine-pitch integrated circuits, tight access areas, and very small pads where a chisel tip would be too wide.
- Bevel tip: A curved surface that holds more solder and distributes heat across wider areas. Useful for drag soldering (running the tip along a row of pins) and working with larger pads.
For most people starting out, a medium chisel tip handles the vast majority of soldering tasks. You can always pick up a conical tip later if you move into finer work.
What Solder to Use
The solder itself comes in two main categories: leaded and lead-free. Leaded solder (typically a 60/40 tin-lead mix) is easier to work with because it melts at a lower temperature, flows more smoothly, and produces shinier joints. Lead-free solder, required in commercial electronics manufacturing in many countries, melts about 60°F hotter and can be a bit less forgiving for beginners. Both types are available as thin wire with a flux core, which is the form you’ll use for hand soldering.
The general rule is to use the lowest effective temperature that gives you a clean, shiny joint. Higher temperatures speed things up but increase the risk of damaging components and wearing out your soldering tip faster. For leaded solder, iron temperatures around 600°F to 650°F work well. For lead-free, you may need to bump up to 650°F to 700°F.