The heat gun will simply not do You need to get the solder balls underneath the chip to 225c and will require bottom and top heat without proper equipment there is no possible way to get it to that temperature and sustain it without damaging other components or the board itself
its not caused by overheating its caused by solder joints the system needs to be reflowed or reballed or have the rsx chip be replaced It is believed that the main cause of the Yellow Light of Death is due to the chip getting so hot during heavy use of the console that the tiny solder points on the GPU liquefies, and over time loses its connection with the motherboard. This is however untrue as in order for the solder to melt the chip would have to reach a temperature of at least 217c which is impossible. The real cause however does have to do with heat, which causes micro fractures in the solder but does not in no way melt it. source: http://xmoddz.com/ps3-repair
The problem is the speaker or camera cables. It's usually the speaker cables—rarely is it the camera. The cable will have a micro tear on it due to the opening and closing of the 3DS. The manufacturer should have protected the ribbon cables.
I just bought a $500 JBC so i have the right tools now I can do the pad replacement, i dont know how to lift pads from the other boards to place them on the damaged board They repair kits i found are a grand at least