Is it OK to use toothpaste instead of thermal paste when fitting a CPU?

I was told many years ago to do this by someone who at the time knew more than I did. The CPU was a celeron in the Pentium 2 era. It ran cooler with the toothpaste between the chip and the heatsink than what it did with nothing between.

Has anyone else ever heard of or tried this? What were the results?

This is the standard "saran-wrap-in-place-of-condom" question. While some toothpastes may provide the correct type of thermal conductivity, "toothpaste" is too big a category to answer the question accurately. Worse, unless you want to make it a fun science project, nobody is going to be testing different types of toothpastes for thermal conductivity.

That said, the answer is probably "yes." Toothpaste is definitely better than nothing, because air (i.e., nothing) is a terrible heat conductor. That said, there are other properties to consider. From Wikipedia

• How well it fills the gaps and conforms to the component's uneven surfaces and the heat sink
• How well it adheres to those surfaces
• How well it maintains its consistency over the required temperature range
• How well it resists drying out or flaking over time
• How well it insulates electrically
• Whether it degrades with oxidation or breaks down over time

I think that toothpaste might work for the thermal part, but you might have other problems in the short- or long-run.

On A Different Note: That said, if you need to stick a note to the wall, you can definitely use chewing gum (after chewing a bit). Sometimes it's hard to get off when your lease is over, though :)

I remember hearing about this at Dan's Data a while back, and he went back and forth with Arctic Silver's Nevin on the issue.

I think the basic idea was that toothpaste will dry up faster than true thermal paste, perhaps leaving you a lot worse off than if there was nothing at all. So, if you like removing your heatsink as much as I do, then no, it's not ok.

It might be better than nothing, but unless toothpaste has unsuspected thermal conductivity, I'd say it's a bad idea.

You also have to consider what the ingredients of the toothpaste might do in contact with your CPU. I suspect it would be pretty conductive in an electrical sense. You don't want electrical conductivity.

Better get some real thermal paste. It's more expensive than toothpaste, but worth it.

Also just used toothpaste on my macbook pro 2011. It had a failing graphics card and being out of warranty I waited until it was truly dead => no boot. I took it apart, cleaned it and removed all plastic. Did a "reflow" of the motherboard in our regular oven at 220 degrees Celsius for a couple of minutes. Applied toothpaste to the cpu and gpu and put it all back together.

After all this it booted right back up. It ran hot for 2 minutes at 90 degrees Celsius. (might have been a diagnostic check after being taken apart, OSX just testing the insides) It now runs at 45 degrees Celsius under normal load. No crashes, no funky broken graphics cards stuff anymore.

It will probably set itself on fire at some point, but more likely because of the failing battery then because of the toothpaste.

Just to be clear: this is an old machine that has been abused for many years. I work as a photographer and this is the machine that travelled with me. So it saw lot's of water, dust, sand, mud and everything you don't want around electronics. Do not try this just because you are too lazy to get the real stuff.

Only badasses may proceed!

Update:

The gpu finally truly died. Well not really, the gpu is perfectly fine, even after months of having toothpaste for thermal paste. The solder connecting it to the motherboard however has too many cracks in it now and a reflow in a cooking oven no longer works.