Dried paste is real. It’s also what people replace when the real problem is a packed heatsink, a dead fan, or a warped bracket. Paste is cheap so it gets blamed. I go by temperatures, not folklore.
How to tell it is actually paste
- Idle temps are fine. Load temps climb and stay high after the fan is already at full tilt.
- The heatsink fins are not packed with dust. If they are, clean first. Paste will not fix a blanket of lint.
- The machine is several years old, or someone already opened it and used a rice-grain-sized dab of compound on a 40mm die.
If the laptop dies in under a minute, I think power, a short, or a fan that isn’t spinning. Paste doesn’t fail that fast unless the cooler is physically off the die.
What I keep on the bench
I keep one decent compound, not a drawer of “8.5 W/mK” tubes with no datasheet. For normal laptops and desktops that aren’t chasing a benchmark screenshot, a known non-conductive paste is the whole decision.
On the bench
A known non-conductive paste (NT-H1 or MX-4 class)
Non-conductive, easy to spread, doesn’t turn into glue in two years. That’s the job. Liquid metal is a different repair with a different way to wreck a board. I don’t use it on a first laptop.
- A small syringe outlasts a hobbyist for years. Do not buy a 30g tub.
- Skip “metal” pastes unless you know the die is isolated and you can clean spills.
Application that does not make it worse
- Clean both surfaces with isopropyl (90%+). The old layer has to come off, including the corners.
- Pea or thin line in the center of the die. The cooler spreads it. Do not paint a mosaic with a credit card unless you are spreading across a large desktop heat spreader and you know why.
- Even mounting pressure. A missing standoff on a laptop cooler is a hotter problem than the compound you chose.
Verdict
I repaste when load temps are high and the cooler is clean and seated. One non-conductive tube is enough. If the fan is silent or the sink is caked with dust, you haven’t earned a paste job yet.