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iFixit wants to fix the soldering iron
(www.engadget.com)
This is a most excellent place for technology news and articles.
IR bottom heaters are usually not strong enough for reballing. They're for boards that are hard to solder, because there's a lot of copper or a heatsink for example.
The bottom heater preheats the whole board, not to soldering temperatures but enough to make soldering a lot easier.