How to Solder: A Beginner's Guide

A soldering iron or station, solder wire (60/40 leaded is easiest to learn on), a stand to rest the hot iron in, and something to clean the tip on (a damp sponge or brass wool). Flux isn't essential if you're using flux-core solder wire, which most general-purpose solder is.

Work somewhere ventilated. Solder fumes aren't something to breathe in deliberately, and rosin flux smoke in particular irritates some people more than others.

The sequence is the same whether you're joining two wires or soldering a component to a board:

• Tin the tip: melt a small amount of solder onto the clean tip so it's shiny, not dull grey.
• Position the two parts you're joining so they're touching or close together.
• Hold the iron tip against the joint itself, not the solder, for a second or two to heat it.
• Feed solder into the heated joint, not onto the iron tip. It should flow and wick into the joint.
• Remove the solder, then the iron, and hold the joint still while it cools (a couple of seconds).

A good joint looks shiny and forms a smooth cone shape around the connection. A cold joint looks dull, grainy or lumpy, and usually means either the joint wasn't hot enough when the solder was applied, or it moved before the solder had fully cooled.

If a joint looks wrong, don't add more solder on top. Reheat it fully, let it flow again, and let it cool undisturbed.

Most early soldering problems come down to one of these:

• Melting solder directly onto the iron tip instead of the joint, which coats the tip but doesn't properly bond the joint.
• Moving the joint before the solder has set, which almost always causes a cold, cracked joint.
• Using too little solder (a weak, thin joint) or too much (a blob that risks bridging to nearby pads or wires).
• Skipping tinning, so the tip is dull and transfers heat poorly.