This instructable shows how to do a DIY rework of BGA components, using a hothair gun and commonly available tools.
Sometimes, expecially if they develop high temperatures during normal operations, the tin solder connecting their pins with board pads tend to become unreliable.
This is due to continuous expansion/shrinking of the component and/or the board caused by heating. To make a professional repair normally an expensive equipment is required, because BGA components have a specific temperature curve for heating, soldering and cooling. But if you're trying to save an old PC or , as in my case, a satellite TV receiver, this instructable might make your day.