Editing Desoldering (section)

===Quad flat packages===
[[Image:Desoldering with hot air.jpg|thumb|Desoldering an IC with a JBC hot air system]]

[[Quad Flat Package]] (QFP) chips have thin leads closely packed together protruding from the four sides of the [[integrated circuit]] (IC); usually a square IC. Removal of these chips can be problematic as 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. The stubs are then easy to melt off and clean with a soldering iron. Obviously this technique  entails the destruction of the IC. 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.

Several vendors offer systems that use heat shields to concentrate hot air where it needs to be, protecting nearby components and avoiding damage to the board or the [[QFP]]. The extractor uses a spring system that gently pulls the IC upward when the liquid stage of solder has been reached. The IC is held by a [[vacuum tweezers|vacuum nozzle]] similar to the ones used in [[SMT placement equipment|pick & place machines]].  This system prevents damage to the pads on the PCB, the IC, avoids overheating surrounding components and blowing them off and also reduces the risk of operator error when using tweezers or other tools that can damage the PCB or IC.

Another way to remove these devices is to use [[Field's metal]], an alloy which melts at around 140&nbsp;°F (62&nbsp;°C), lower than the boiling point of water. The metal is melted into the solder joints of the device, where it remains liquid even once cooled down to room temperature, and the chip can simply be lifted off the board. This has the advantage of not damaging the PCB or the IC, although the solder joints must be carefully cleaned of any remaining Field's metal to maintain solder joint strength after resoldering.