On the heatsink for my T400, thermal grease was used for the CPU and the GPU. There is a third component though covered by the heatsink - which I'd have to look up to know what it is and does. Anyways, instead of thermal grease, there is a thermal pad there.

In removing the heat-sink to upgrade the CPU, I've noticed the thermal pad got slightly dusty and there may even be what appears to be a fine hair or thread of some sort stuck on it.

Should I purchase a replacement, and if so - where can I purchase one? Thermal pads can't be cleaned can they?

I plan to use Arctic Silver 5 on the CPU and GPU instead of the poor quality grease that was there before and have used Arcticlean remover and the purifier to get rid of the existing grease on the CPU and GPU and will apply Arctic Silver in between those components and the copper heat-sink, but the heat-sink has been designed to use a thermal pad on the third component, otherwise I'd just remove it and use arctic silver for it too. So I need to either use the current one or buy a new one.

Your help is appreciated.

Try cleaning it off with some rubbing alcohol and a something that won't leave any fibers/lint behind.

How about a coffee filter?

Is 70% isopropyl alcohol strong enough, I don't think they have 90% or above locally, I'd have to order it.

I also have Arcticlean Purifier.... which I think is primarily alcohol.

70% is just fine, the rest is just water (as long as you don't have a dyed one). I would avoid using the Arcticlean on it just because it would be overkill and I don't know if it's safe for thermal pads.

I cleaned it with alcohol, but that removed a tiny amount of the material itself. To make up for it, I applied a very thin layer of Arctic Silver to the component.

While I don't usually mix thermal products, I figured that in this case it probably wouldn't hurt it.

Put everything back together and booted... works. Will have to wait until I know how well it's cooling. The only snag I ran into was that I had trouble remembering where the antenna (presumably wifi) cables go. I'll have to go back in there and fix it once I figure out where they're supposed to go.

Anybody know what that chip is anyways?

As long as it didn't create pits or cracks it should have been fine.

It gave it a slightly less than perfectly smooth texture. This was another reason I applied a very thin layer of Arctic Silver.

I still don't even know what the chip is.

You can see it here:



It's the chip almost dead center in the board. If you look at the CPU socket, to the immediate right there are 2 major chips. The one to the immediate right of the CPU (and in the picture with thermal grease on it) - I believe is the GPU. The chip below it though, to the left of the Intel branded IC - is the one in question. It has some sort of core IC, surrounded by small SMT components on a board about the same size as the CPU. It can also be found by looking directly above the memory slots, and again of the two chips immediately there, it's the one to the left.

What is that, and how much heat does it generate?

That's the northbridge and it can. They are also designed to take a lot of heat (a lot like GPUs).

ah.

For some reason I thought most computers over the last few years didn't have a northbridge.

In case someone else is going to look for a thermal pad, I'd suggest using Fujipoly 6.0 W/mK.
Anything better than that is going to be ridiculously expensive.
Frozencpu.com carries that stuff - just pick the thinnest pad you can get away with.
The thicker the pad, the worse it works.

why is there a thermal pad there to begin with? Why not make the heatsink sit right on top of it so thermal grease can be used. Is it to contain the heat locally more than to cool the component? I didn't understand that aspect of the design.

Computers still and will pretty much always have northbridges. The next big thing is on die northbridges. I think AMD is shooting to be the first one to do it when they go to AM4, but we will see.