Desoldering and Rework: Getting a Part Off Without Lifting the Pad

Counter-intuitively, the first move in removing solder is adding some. Melt a little fresh solder into the old joint and let it mix. Old solder has lost its flux and often sat for years; it melts sluggishly and unevenly. Fresh solder brings fresh flux, lowers the effective melting point of the mixture, and makes the whole joint go liquid at once instead of in patches. This one habit is the difference between a clean removal and four attempts, and four attempts is what lifts pads. It matters most on exactly the boards you most want to save — old ones.

Cock the pump, melt the joint fully with the iron, bring the nozzle down beside the tip, then lift the iron and fire in the same movement. The window is under a second. Fire while the solder is still liquid and it leaves in one go; hesitate and it freezes, and the second attempt starts from a worse position than the first. Practise the sequence on scrap before you need it on something you care about. The pump is the right tool for a through-hole with a lead in it, because it can pull solder out of the barrel of the hole where braid cannot reach. Empty the pump regularly — packed solder inside it kills the suction and you will blame your technique.

Lay the braid flat over the joint and press the iron down ON TOP of the braid. Heat travels through it, the solder melts and wicks up into the copper mesh by capillary action. Lift braid and iron together. Never lift the iron first — the solder freezes and solders the braid to the board, and freeing it usually takes the pad with it. That single error accounts for most braid-related damage. Braid is what you use on a surface-mount pad, on a track, and to clean the last film of solder off a through-hole the pump has already emptied. Cut off the used length: solder-saturated braid absorbs nothing and just conducts heat into the board.

After the part is out, inspect the pads under a lens and put the meter on continuity between each pad and the next point on its track. A pad can look intact and be lifted — the copper still sits in place while the track that fed it has cracked where it leaves the pad. Continuity finds that in seconds; the eye does not. If a track has broken, a short wire soldered from the pad to the next via or component leg restores it, and that repair is entirely normal. What is not recoverable is a pad that has come away and taken its via with it on a multi-layer board, which is the reason for all the care in the earlier steps.