You would think so, wouldn't you? As I recall, I tried lower temperatures first and it just took too long for the solder to loosen. My back of a beer soaked envelope explanation would be that the heat is conducting away at some rate and so one needs a higher temperature source than the target temperature. But beats me. The 600F setting is the one that gets the chips loose in about 2 minutes. The heat gun could be poorly calibrated. It was inexpensive but gets the job done. Interestingly, if I'm doing a bunch of boards, e.g. pulling the flash off of cheap ATA-66 cards, after the first card the following ones go faster. Either the heat gun takes a while to reach its set temperature, or my work area gets hot and helps the boards along or something. I use a 1/16" sheet of sheet metal as a work surface. I figure it's anti-static protection and fairly impervious to mechanical, chemical and thermal insult. I've heard of those, but they seem to cost multiple hundreds of dollars. I like the < $40 heat gun + modeling clay solution. That's a little bit of hyperbole as I also have dental picks and the Chip Quik set for the big chips and a nice bottle of resin. With those and a 15W and a 40W soldering pencil I manage. I thought there was bismuth involved but the memory is moldy. It melts/mixes in with the existing solder and lowers the melting point. That's the point behind the stuff. It's fairly expensive, but very little of it is needed per desoldered chip. And four beads of the stuff makes the big QFPs come off soooo much easier. Jeff Walther