adalbert wrote:Well, I think that hot air gun should only be used for recycling slots and big components from not-working hardware. Excessive heat can cause deformation and bending of the PCB, so the internal layers can be broken making the mainboard unusable... Once I tried removing ISA slots from broken mainboard and the PCB looked like it was starting to melt. You should have tried cutting the pins of that dead RTC chip using a flat knife, then removing the pins one by one with soldering iron.
Cutting the pins might help a little, but the main culprit is the thick multi layered laminate used in motherboards. It just leads away heat too well.
I usually preheat motherboards from the bottom side with the heat gun, to 130-150 deg C, taking care to not heat any electrolytic caps or plastic details I want to keep, then desolder as usual with the soldering iron. Makes it a whole lot easier.
Half-Saint wrote:
Cutting off the dead RTC chip wasn't an option without risking surface damage to the motherboard because of chip's position. I used a very small nozzle and a temperature of 400C to heat up just the area around the pins but I foolishly forgot to apply aluminum foil on the rest of the board. When I flipped the board I found that the BIOS chip was quite warm to the touch. Visual inspection doesn't reveal any deformities.
Don't worry too much, IC's are usually made to withstand the heat they're subjected to when wave soldering PCBs, with broad margins 😀