Using Duet2 and Volcano heaterblock as solder aid?

[o_lampe]

Hi guys,
I have to replace a SOP8 chip on an expensive PCB and it has a thermal pad below the chip.
The usual way to heat it up would be a quarz-heater on the backside with a certain temp to preheat the GND plane of the PCB.
But I don't have such a device at hand, so I thought a volcano heater block placed below the chip in question would be good enough for a one-time solution?
The heaterblock wouldn't touch the PCB, so I'm struggling to figure out a good target temp.
Where would I put the thermistor, or should I use a second thermistor on top of the PCB?

Any hints would be welcome

[tas]

@o_lampe I nominate you for the most novel use of a Duet ever.

Try ChipQuik SMD Removal Alloy (SMD4.5). You may not need to heat the board at all.

Clean it all off thoroughly before trying to solder the new chip in place.

[dc42]

@o_lampe that sounds viable. Put the thermistor in the heater block as usual. Alternatively, do as I did and buy a cheap electric hotplate, and put the PCB on top of that. Use a multimeter thermocouple probe between the hotplate and the PCB to monitor the temperature.

I heat the PCB to between 120C and 150C (I have put a mark on the hotplate control knob that gives me this temperature), let it soak for a couple of minutes, then use hot air to remove the chip. Use minimal force to lift the chip, otherwise you risk lifting PCB traces. Practice on a discarded PCB if you haven't done this before.

[JuKu]

For a one off job, the solution @dc42 gave would work. You can even do it on your kitchen stove, if you have a good fume hood. A piece of aluminum (or iron, if induction) will help regulate the temperature. Do practice with a scrap board first!

[o_lampe]

@JuKu A kitchen stove sounds like a good idea, too. But I can't sit there and I need a relaxed position for this job.