Rework station recommendations

Very good idea to practice, practice, and practice some more on salvaged boards until you get competent with new tools. You didn't notice the solder had reached the molten state because there's so little of it used to solder components.

The typical lead-free solder has a melting point around 217 degrees C, so you'll have to get the leads and pads up to that temperature before trying to remove the component. The reason why you need a much higher temperature is because you want to get the solder joints to the melting point as fast as possible. If the hot-air gun is set to a much lower temperature, it'll take a longer time to reach the melting point. The longer the time to raise the temperature of the leads/pads will increase the overall temperature of the component, possibly past the point of destruction. So the technique is to heat it up fast, remove the part and hot-air gun, then put the part where it can cool off.

Now, if you're removing a part that's already fried due to some other reason, no worries then. Just don't damage the board by overheating the pads and causing them to lift off. If that happens, your headaches are just beginning on this repair.

A few basic things I would like a hot-air rework station to have:

1. A min temperature range of ~100C. This allows you to use the gun for heat shrink.
2. A max temperature of at least ~350C, though higher is better (within reason, of course). I think most low-end hot-air rework stations are spec'd at ~450-550C max, but don't quote me on this.
3. have the ability to change out nozzles, in particular smaller nozzles for focusing the air stream and larger nozzles if you need to soak a region (say a large BGA package or a packages with large exposed pad heat sinks).
4. Some temperature regulation. It doesn't have to be too precise since it's dependant on air flow and distance of gun from the target, but I would imagine better than 10C accuracy is good. You can probably even get away with less accurate temperatures.
5. Adjustable air speed. It's no good if your gun blows all your small SMD parts away, or doesn't have the oomph to transfer enough hot air to the target.

Other bonus features:

A. "Auto-shutdown" which will automatically powerdown the unit if you place the gun back into the holder.

B. Some units have a cooldown before shutdown feature which will turn the heater element off but leave the fan on until the temperature drops below a certain temperature. I believe the theory is that this will extend the life of the heating element.

You can check out Dave Jone's EEVlog #167 for a review of the Atten 858D+. He explains the basics of what a usable gun should have.