Laptop HDD (100565308 Rev A) BIOS chip swap - chip won't come off?
The best thing to do is to use hot air rework with a thermal profile with solder that is high temp. The profile ensures that the solder can get hot enough to remove the chip, but only briefly.
In my experience some kind of flux also can help spread heat, and lower the temp of the solder, so surrounding the chip with some kind of flux can help remove it.
If the chip has a thermal pad with vias a soldering iron can be used on the bottom and hot air on the top to remove the chip.
With lead free solder, 300C won't be enough to bring the solder to a melting temp, because 300C is what the pen temperature is at, and as the heat spreads out on the PCB, the temperature drops. Even with hot air rework, I've found that I need 330 to 360C to remove IC's with lead free solder (but be careful as this can violate absolute maximum ratings).