I finally decided to build a PID hotplate. PID controllers are very cheap (see EBay and Amazon), and so are cartridge heaters. Today I drilled my aluminium block:

_________________
In theory, there is no difference between theory and practice. In practice, there is. ...Jan van de Snepscheut

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

It's a chunk of aluminum that can be heated up using the two heater cartridges in the picture. You put the PCB on the block, with the BGA in its correct position, and then you crank up the heat. The heat will transfer through the PCB, and melt the solder balls. At least, that's what I figured.

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

It could be done in a reflow oven, but this is a good alternative. One of the problems with an IR oven is that the heat for the balls has to go through the package, which will then become very hot. This is especially problematic for lead-free soldering. In the industry, these are best done with a vapor phase reflow oven, but these are not within reach of the hobby budget

A hot plate is also nice and small, so you could put it on your desk and watch the solder melt.

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

Thanks Arlet, I couldn't have explained better myself.

A skillet will work, although not as well as it is usually made of thinner material and the heater runs in a loop, heating unevenly. A skillet also has a very annoying rim that burns you every time (I have scars to prove it). Flat griddles are more convenient, but generally don't heat well enough (I had to keep one board on it for about 10 minutes before anything melted).

A PID controller with a thermocouple sensor will keep the temperature exactly where I want it.

In addition to replacing an oven as Arlet described, it can be set to a lower temperature to preheat the board closer to solder melting point, and use an iron or a hot air pencil to push solder over the melting point very quickly and with low thermal shock to the parts.

_________________
In theory, there is no difference between theory and practice. In practice, there is. ...Jan van de Snepscheut

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

Two 300W cartridge heaters should do the trick. The end result should look something like this:

For more info, see this http://mightyohm.com/blog/2009/01/diy-pid-controlled-soldering-hotplate/

_________________
In theory, there is no difference between theory and practice. In practice, there is. ...Jan van de Snepscheut