Desoldering - Quad Flat Packages

Quad Flat Packages

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.

A system under the JBC brand uses extractor shields that concentrates heat where it needs to be, protect surrounding components and avoids damage to the board or the QFP. The system takes advantage of the properties of solder by melting it with hot air. The extractor has 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 nozzle similar to the ones used in 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 removes the risk of having operator errors by using tweezers or other tools that damage the PCB or IC.

Another 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 140 °F (62 °C) — less than water's boiling point. Once it's applied to all the leads, it stays molten, and the chip can simply be lifted off the board. This has the advantage of not damaging the PCB or the IC.