Bought a NUC 13 Extreme i9 a few months back and generally it's been pretty good. However, it has an issue with audio crackling that I eventually traced to the PCH temperatures (mine runs at 78-80C at idle with the Balanced power plan, and 95-105C at idle if I set the High or Ultimate power plan - regardless of what the NUC software controlled power plan is set to). Since I've not had the time to take mine apart and look into this, I did some digging and I think I have identified the problem.

If you look at this image (taken from this page) you can see that the Z690 chipset's only cooling appears to be a tiny bit of aluminum plate that's screwed into some press fit stand-offs in the backplate of the NUC module. And whilst you can see there is a thermal pad on the plate, there doesn't seem to be any suggestion that the plate has a thermal pad behind it, and even if there is - it's not an ideal thermal conduit to the backplate. The second issue is that this part of the backplate is pressed against the back of the PSU, with a very small gap and almost zero airflow. And apparently, the Z690 has thermal problems on ATX boards with heatsinks, a million fans, and good airflow...

Annoyingly if you look on the Intel forums for this issue, there is someone who had the same problem and solved it by replacing the PCH heatsink on the picture I linked above with a copper plate. and better thermal paste, but left no details.

So based on what I know, I think I have several possible options:

1. Replace the thermal pad (or pads) on the little heatsink with higher-performance thermal putty
2. Remove the heatsink plate entirely and bridge the gap to the backplate with more thermal putty.
3. Replace the heatsink plate with a larger copper disk and use thermal putty on both sides
4. Replace the heatsink plate with a larger copper disk, but solder additional shims to the bottom of the plate to bridge the gap between it and the backplate.

My questions are:

1. Has anyone else encountered the same problem and if so, what steps worked?
2. Am I actually correct about what the problem is or have I misunderstood something?
3. Which of the solutions is the most likely to work?
4. Does anyone have clearer pictures of this area? Or any idea about the thickness of the little heatsink plate? I don't have the free time over the next month or so to spend a day taking mine apart, but there might be someone reading this who has one cracked open already.