Desoldering

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Solders can be removed using a vacuum plunger (on the right) and a soldering iron.

In electronics, desoldering is the removal of solder and components from a circuit for troubleshooting and repair purposes. Electronic components are often mounted on a circuit board and it is usually desirable to avoid damaging the circuit board, surrounding components, and the component being removed.

Specialized tools, materials, and techniques have been devised to aid in the desoldering process.

Desoldering tools and materials include:

Desoldering braids
Heat guns
Vacuum plungers (solder suckers)
Removal alloys
Removal fluxes
Vacuum and pressure pumps with specialized heater tips and nozzles

[edit] Quad Flat Packs (QFP)

QFP chips have thin leads closely packed together protruding from the four corners of the integrated circuit (IC); usually a square IC. Removal of these chips can be problematic. It is impossible to heat all of the leads at once with a standard soldering iron. It is possible to remove them with the use of a razor blade or a high-rpm craft tool,simply by cutting off the leads. This technique however, can lead to the destruction of the IC. The stubs are then easy to melt off and clean with a soldering iron. Another method is to use a heat gun or pencil butane torch and heat up a corner, and gently pry it off, working the torch down the leads. This method often leads to traces getting lifted off the PCB where a lead did not get heated enough to cause the solder to flow. The easiest way to remove one of these devices is to use Field's metal. Take some of the Field's metal wire, and solder it into all the leads of the chip. Fields metal melts at around 140ºF (62ºC) — less than water's boiling point. Once it's applied to all the leads, it stays molten, and you can simply lift the chip off the board and finish your clean up work. This has the advantage of not damaging the PCB or the IC.