Before delving into through-hole soldering or surface mount soldering, it can be helpful to review joining two wires, which can help reinforce important techniques. Make sure the iron is turned on and set at the appropriate temperature (about 700 degrees F for leaded solder, and 800 degrees F for lead-free solder) and the tip is tinned.
STEP 1: STRIP WIRES
Use the wire strippers to strip the wire insulation off the last ½”-1” of each wire to be joined. Match the wire diameter to the appropriate hole on the tool, clamp down and pull away towards the end of the wire to remove the insulation.
STEP 2: TWIST WIRES
Twist the wires together. This will make it easier for the wires to be joined as they won’t fall away from one another when soldering. I prefer to align them parallel to one another and then twist them which will reduce stress concentrations as opposed to twisting them perpendicularly. At this point if you have helping hands you can place the wires in the helping hands.
STEP 3: SOLDERING
When soldering wires, the soldering iron is always brought to the wires first to heat them up for 1-2 seconds, and then the solder is brought to the heated wires and melted. The solder will flow on to the wires and between them with the help of the flux in the wire core.
The iron should not be held against the wires for more than 3-4 seconds total. If an attempt is unsuccessful, pull the iron off and let everything cool for about 10 seconds and try again.
The solder is stuck to the wires.
If the solder is stuck on the wires, simply bring the iron to the junction of the wire and solder, heat it up, and pull the solder away.
The insulation on the wires has melted.
This is not a huge problem, though it can be an issue if not addressed. The insulation on the wire will melt if the wire is too hot (soldering iron against the wire for too long) or if the iron brushes the insulation. If you need to fix it to prevent a short circuit, you can use heat shrink or electrical tape.