I don't think that you fried the BIOS chip since the chip itself was on the top side and you used the hot air gun on the bottom side, but the hot air gun maybe caused other solder pads to melt and caused shorts or bad contact.
I would check for continuity on the traces and component legs nearby the area.

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.

Do you know that the board was working before the chip was replaced? Have you tried putting the old chip in the socket?

shamino wrote:

Do you know that the board was working before the chip was replaced? Have you tried putting the old chip in the socket?

The board has been sitting in a box for at least six months. Prior to that, it would POST but it wouldn't save BIOS settings so I couldn't get it to boot from a hard drive. I assumed that the board was probably fine and that the RTC battery was dead. I haven't tried using the old chip because I cut off some of the legs while desoldering...

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 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.

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 😀