Before you attempt this, consider if you really need a different cooler. Then read through the text, take in what I am subtly trying to convey to you, and then consider if you really want to do it.
Also, common sense at every step applies.
Additional trivia: I used a torque screwdriver and screwed in all screws related to CPU mounting (IHS, Noctua bracket, Noctua heatsink) with 0.4 Nm torque. I also used (probably wasted) a Kryosheet, so your results may vary.
1. The great disconnection
Disconnect everything, everywhere on the motherboard, and remove it. It is screwed in with 4 screws and pretty well stuck in there. Remove the long metal bracket at the front (4 screws), so you have some “wiggle” room. Mine was rather reluctant to get free from its IO shield. With the new acquired space at the front, gently pull back and up. Somehow. You’ll find a way.
Unscrew and unmount the stock CPU cooler. Take out the screws from the IHS (the cpu heatspreader), since it is screwed to the backplate.
2. Backplate Raid Boss
Remove the backplate. You will soon think “He just said that.”. The backplate is glued on with what I can only describe as military-grade adhesive. You will need a heat gun and maybe even a solvent (be careful with that, you don’t want to dissolve the motherboard. Test it on a small, free area first to see if it damages it). And take your time. It took me an hour to grind its HP down to 0.
When you have the backplate off, check how your fancy new CPU cooler is mounted and think about it.
But either way, you will want to put the stock backplate back on, simply because it is the only way to get proper seating for the IHS. Believe me, I tried without (no screws and backplate, just clamped on by the Noctua mounting). It doesn’t take power spikes well, just not good results. But to be able to mount (for example Noctua stuff) over the bracket, you have to literally hammer out the screw sockets that the stock cooler was screwed into.
This is by far the most fun step, so enjoy it.
3. ZimaCube Assemble
Screw the backplate and IHS back together, they are made for each other. The IHS might have fallen off during the big backplate battle. Repaste if necessary. You should be able to mount whatever cooler you have over this (again, better think about it beforehand and adjust accordingly, I used a Noctua NH-L9x65). Don’t forget the thermal paste.
When you have mounted your new, probably overkill cooler, you are almost done. Almost, because now comes the second most unnerving part of the entire process. Remounting the motherboard.
Most notably, reconnecting the flat data cable that connects to the drives. Again, take your time and be careful with it. It’s almost certainly the most fragile part of the entire device. I must have had it not seated 100% correctly. First, Unraid didn’t detect the nvme’s anymore. Then after reboot my parity drive got kicked out of my array due to write errors. Reseated the cable, rebuild parity, all good now. Totally not panic-inducing.
4. Epilogue
Congratulations hero, you’ve done it! You have rescued the princess and the village is saved.
You have a new cooler, how cool! I will never, ever touch these components again.
The highest I’ve seen the CPU is 62-64 degrees after constant, full load with boosting etc inside an uncomfortably warm room. 70 degrees when I completely hammer the iGPU as well. It will now probably live longer than me. Good luck and godspeed.