I am desoldering an IC with a 20 watt iron and desoldering pump. The ICs are soldered with lead free solder and I have trouble getting the joint to wet;. With minimal tools how can I desolder lead free well?
You can use a product called ChipQuick on each pin. ChipQuick is a very low melting solder (also available lead free) that forms a low melting alloy with the lead-free solder that is there. Imagine using something like using solder made of Wood's metal. Once you get the part off, you can use solder wick to clean the pads. Then re-solder in the usual manner. A good flux helps in the removal too.
A 20W iron is unsuitable for IC desoldering, especially on double sided PCBs. A 60W iron is definitely superior to a 40W iron for desoldering, with all the irons I've tested. A 20W iron is not good for much at all.
Check ebay for "60W temperature controlled soldering iron" you can get one quite cheap.
I heat the whole board over a gas ring and pull out the chips quickly with a puller. I have taken 49 chips out of a board and replaced them. And the whole module worked. It was quicker and faster than trying to work out the fault, as no circuit was available.
I have quite a large collection of old chips unsoldered many years ago mostly from Computer boards. Terrible as it may sound I removed them all using a small blow lamp using meths and screwdrivers. I have never found a chip that failed, but the burning of the boards caused a stink !!