Guide · Beginner · about 30 minutes, plus practice

Soldering guide

Soldering joins parts permanently with a little melted metal. It is easy to learn and safe with a few simple habits. Learn the tools, the five-second technique, and how to tell a good joint from a bad one at a glance.

Safety first

The tip is about 350 °C. Always put the iron back in its stand, never on the bench, and hold it like a pen, well back from the tip. Unplug it when you stop.
Wear safety glasses. Solder can spit, and clipped component legs fly across the room.
Don’t breathe the smoke. It is mostly flux fumes, which irritate the lungs. Work in a ventilated room, with a fan or fume extractor drawing the smoke away from your face.
Wash your hands afterwards, especially with leaded solder, and don’t eat or drink at the bench. Lead-free solder is the safer choice for beginners.
Only solder circuits that are switched off and unplugged, and only low-voltage projects. Never work on mains-powered equipment.
Young learners should solder with an adult supervising.

What you need

A temperature-controlled iron with a chisel or conical tip, and a stand.
A damp sponge or brass wool to wipe the tip clean.
Solder with a flux core, about 0.7–1 mm thick. The flux cleans the metal as it melts so the solder flows and sticks.
Flush cutters to trim legs, and safety glasses.

Helping hands or a small vice to hold the board.
Desoldering braid (wick) or a solder pump to fix mistakes.
Something to practise on: a cheap practice kit, or stripboard and a few spare resistors.

Temperature: about 320–350 °C for leaded solder and 350–380 °C for lead-free is a common starting point. Check your solder’s recommendation; hotter is not better, as it burns the flux and can lift the copper pads.

Making a joint: about five seconds

Tin the tip. Melt a little solder onto the clean tip so it shines. A shiny tip carries heat well.
Heat the joint. Touch the tip to the pad and the component leg together, for about one second.
Feed the solder to the joint, not to the iron, on the opposite side from the tip. The hot metal melts it and it flows around the leg.
Remove the solder first once there is enough to make a small cone, then the iron.
Keep still for a couple of seconds while it sets. Movement now makes a weak, grainy joint.
Trim the leg just above the joint, pointing the cutters away from your face.

A good joint is smooth and shiny (lead-free solder is a little duller), shaped like a small volcano, and you can still see the outline of the leg. The solder has flowed onto the whole pad.

Joint inspector

Look at each joint and choose what is wrong with it, if anything. Each answer explains the cause and the fix.

Fixing mistakes

Desoldering braid (wick): lay the braid on the joint and press the hot tip on top. The braid soaks up the melted solder. Lift braid and iron together, then trim off the used part. Best for bridges and too much solder.

Solder pump: cock it, melt the joint, then put the nozzle on the solder and press the button: it sucks the solder away. Best for clearing a hole to remove a part.

Reflowing: a cold or grainy joint often just needs reheating, with a touch of fresh solder (for its flux), until it flows and shines.

Lifted pad: too much heat or force can peel a copper pad off. Bridge the gap with a short wire to the next point on the same track.