I installed a Ryzen 5 5600X3D with a Noctua NH-U12S cooler, but temperatures were much higher than expected: around 90°C in games at only 60–70% CPU usage, even with the case panels removed and the fans running at full speed. After removing the cooler, I found a small piece of metal wedged between the cooler and the CPU's integrated heat spreader. I removed the metal, but it left a gouge and burr in the heat spreader. The damaged spot is uneven enough to catch a fingernail or the edge of a credit card. I lightly used coarse sandpaper and remounted the cooler, which helped somewhat, but temperatures still reach 75–85°C with spikes to 90°C at roughly 55 watts. I'd like to flatten the area while removing as little material as possible. Is finer sandpaper appropriate, or should I use a diamond file, machinist's stone, or another method? The gouge is near, but not directly over, the CPU die area.
4 Answers
If there is a raised burr, a machinist’s stone or very fine abrasive on a genuinely flat surface is safer than attacking it with a file. The usual process is called lapping: tape 600-grit wet/dry sandpaper to a sheet of glass, make light passes with the CPU held flat, and inspect constantly. You can move to finer grit afterward, but stop as soon as the burr is gone. Protect the socket and contacts from abrasive dust, then clean the heat spreader with isopropyl alcohol.
CPU lapping can work, but it’s easy to turn a small defect into a larger problem. It can remove the printed markings, affect resale value, and potentially make the heat spreader uneven if the CPU isn’t kept perfectly flat. I wouldn’t use a diamond file unless there’s a severe raised section that cannot be addressed with a stone.
Those temperatures may not be caused entirely by the gouge, especially since the damaged spot isn’t directly over a die. A cooler mounting issue, uneven contact, trapped paste, or a poorly seated backplate could be contributing. Try checking the paste imprint after removing the cooler and verify that all mounting screws are tightened evenly in alternating steps before committing to more lapping.
If no part of the gouge is raised above the rest of the heat spreader, I’d seriously consider leaving it alone. Clean it thoroughly, apply enough thermal paste to fill the depression without trapping air, and reinstall the cooler carefully. A small void away from the die usually shouldn’t cause a major temperature problem. Before removing more material, double-check cooler mounting pressure, paste coverage, fan direction, and ambient temperature.
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