I'm reusing the thermal pads - the Internets suggest that the clearances for the memory and voltage regulators are too large to sensibly use thermal compound, and I don't have any replacements - but that massive lump of thermal compound in the middle has to go.
Well, if Amazon will send me a pointless plastic card... anyway, with that, some more lens cleaner, and some elbow grease I cleaned all the gunk off. That left a pretty sorry-looking copper block, but it'll have to do.
I also removed the heatsink from the cover to evict any dust bunnies from the heatsink fins.
There were some casualties. Only the R remained attached, and while I saved most of the letters one of the E's is missing, presumed eaten by the Roomba. Meh, I can't be bothered to reattach them.
Anyway, while I was doing that the card cooled down enough that I could now apply the Arctic Silver! Again the pointless plastic card becomes useful:
And that's a more-or-less even coat. Again, it'll have to do.
Before screwing everything down I thought I'd better do a test fit first with the heat sink and check that it's thick enough - again, the Internets suggest that there can be a large gap.
That's... quite a gap to achieve that. Let's add a bit more and try again...
Still more needed? Eventually I ended up with this, and in the process managed to get a bit of the thermal grease on the surrounding capacitors. Oops. Now, Arctic Silver 5 isn't conductive (despite the name and what half the Internets think), but it is slightly capacitive which can cause issues if it bridges any pins. Hopefully this won't be an issue here:
All that remains is to tighten everything down, reinstall the card, and hope for the best!