I replaced the thermal paste on my switch, and then after i tried turning it on, my switch was bricked on a black screen, it charges and while i try entering recovery mode, it just turns off.
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First thing I would do is retrace all your steps. You don't need to do much disassembly to get at the heat sink, but I would just make sure all your cables look like they are connected. Aside from that I would look around the heat sink and verify that no components are missing. The components in that area related to power for the CPU. So if any of those parts were disturbed, you could get into issues booting.
If all else fails, make sure your re-paste job was good. Add in some pictures with your question if need be.
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which recovery mode do you mean? The one accessed by holding (VOL+) + (VOL- ) + (Power) or RCM?
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