Thanks to all the folk providing information and on-hands experience to us readers. I used the given information to replace a faulty fan. My Switch overheated after about 30 minutes (depending on load). While I was at it, I also took a closer look at the cooling layout and performance. I found that:
TL
R: Pads added on top of the heatpipe and the RAM cover. Paste for the SOC. Shim left alone. Pad sizes used were 1mm on top of the heatpipe towards the aluminium shield and 1.5mm on top of the cover over the RAM (both GELID 15w) - ensuring 100% contact but also resulting in a very tight fitting of the shell. But no actual denting though!
Detailed:
1. Factorywise, the Switch does not connect the RAM directly to the cooling cycle. But, judging from inspection, it may well be an indirect and very latent connection heating up that cover (silver shielding also holding the shim) over the SOC and RAM through natural convection. The heatpipe (and convection again) will then transfer some of that heat to the aluminium case shielding (the red paste is also important for this). The fan does most of the work though of course.
a) In order to facilitate this, I added some pads above the RAM (on top of the cover only, for it seems that direct contact may even be counterproductive by stressing the ram with excessive heat!)
b) I replaced the red paste (on top of the heatpipe) with a cooling pad also. In my opinion, pads are better suited in these two places overall. Makes it easier to service while not loosing any critical cooling performance.
--> I thus agree with all the people b4 me that strongly stress retaining the connection between the heatpipe to the aluminium skin (the red paste). This allows the Switch to stay silent a bit longer under low loads - which is quite ingenious actually. And it helps take away some of the heat under heavy loads - which is rather cosmetic though.
2. I left the shim. Reasoning being that its purpose is to ensure even contact. And there is also some white tape at its edges shielding some parts from making contact to the heatpipe. Yes, direct contact may be prefered here (using liquid metal if done safely!), but imo it is not worth the effort and additional risk.
a) I applied thermal paste to the die (ensuring total coverage) and to the contact plate of the heatpipe (which is by no means 100% uniform quality btw). Paste seems more suited to ensure that all little gaps are filled here.
Overall, the Switch is not meant for sustaining high performance loads without compromising fps. It can not cool itself adequately enough for that overall.
The switch essentially tries to sustain temperatures by "locking" the area around the SOC and PCB to 60° C. It does so by lowering the load on the chip (e.g. limiting to less fps). Meanwhile the skin actually absorbs some of that generated heat. In theory, this should also have a limit of 60°. But I have not tested that.
3. What I also did afterwards is to increase fan speed a step. I hope this helps with sustaining fps a little bit longer with those high load applications (e.g. BOTW).
