Thermal paste issue/question

[xbdestroya]

Well here's my situation.

Normally I use Artic 5, but my new Zalman 7000 only makes contact with my A64 2800 on the edges of the AMD heat spreader. Soooo.... right now my CPU is idling at about 48 C.

It's not going to end my computer, but it's still a little warm.

Now, there cannot be much space between the cpu and the heatsink, so I was thinking of getting a thermal pad and using that instead, as it will probably (I think) make contact.

Any ideas or suggestions? Or any higher performance products anyone can suggest that don't have to be spread on in a super thin layer?

 

[Lord Banshee]

The center of the die is probally alot closer then you think. ALL heatsinks are flat so if you zalman only touchs the edges than all heatsinks will only touch the edges. Form what i read you only need to put the thermal paste in the center of the die as thats where the real die sits(right under it) but heat will transfer throughout the metal covering but it will become the hottest first in the center.

So maybe you put a alittle to little in on the chip...

 

[xbdestroya]

Well, don't know about that -

I spread it all over the cpu, of course, and used a clean edge to wipe the excess off, as one is supposed to do.

But I know for certain that the center's of my cpu and heatsink are not touching each other because when I lift the heatsink off the cpu, there's a very noticable area where the silver has been disturbed on the edges, but the center of the cpu looks as tranquil as ever. Add to this that there is NO silver compund on the centerof the heat sink, and I think that proves my situation.

 

[Lord Banshee]

Here is how articsilver says to apply their compund
http://www.arcticsilver.com/arctic_silver_instructions.htm

"On an Intel P4 or Athlon64 type CPU with a large metal heat spreader, put a small amount of Arctic Silver onto the center of the heat spreader as shown in the photo.
Only a small amount of Arctic Silver is needed

P4- About the size of an uncooked grain of short-grain white rice or 1/2 of a BB.

Athlon64- About the size of one and a half uncooked grains of short-grain white rice or 3/4 of a BB.


RECHECK to make sure no foreign contaminants are present on either the bottom of the heatsink or the top of the CPU core. Mount the heatsink on the CPU per the heatsink's instructions. Be sure to lower the heatsink straight down onto the CPU.

Once the heatsink is properly mounted, grasp the heatsink and very gently twist it slightly clockwise and counterclockwise one time each if possible. (Just one or two degrees or so.)

Please note that some heatsinks cannot be twisted once mounted.

Our testing has shown that this method minimizes the possibility of air bubbles and voids in the thermal interface between the heat spreader and the heatsink. Since the vast majority of the heat from the core travels directly through the heat spreader, it is more important to have a good interface directly above the actual CPU core than it is to have the heat spreader covered with compound from corner to corner. "

Pictures on the link

 

[xbdestroya]

Excellent link - thanks a lot!

 

[MarkHark]

One thing some people also recommend would be "lapping" or "sandind" your heatsink surface over a flat glass surface, until it is perfectly flat. You can search for quite a few threads where this process is discussed in details, including which sandpapers to use, either here or at amdforums.com, but there seems to be a lot of work involved in that, so if you wanna take the easier route, just get yourself some good thermal pad or try reapplying AS5 as Banshee told you.

For good thermal pad recommendations, I'm sure you can find many different opinions (try the "cases and cooling" or the "overclocking" forums at amdforums), but Shin Etsu seems to be a good starting point, as recommended by AMD itself.

 

[xbdestroya]

Well, I have to say my Zalman is a mirror finish kind of product.

No need for smoothing there.

Truth is, I'm not quite sure exactly why it doesn;t touch the center. Maybe some sort of warp on the heat spreader? Or maybe the cooler when it's tightened onto the mounting bracket, I don't know. It is very weird, that much is true.

 

[Lord Banshee]

What MarkHark was talking about is not smoothing your heatsink but the heatspreader of your CPU. There is alot of work to be done and might not help unless you get it completely flat... You can also F'up your CPU too. So try at your own will.

Did you try the method include in the link... Did it help any.. Also are you letting it cure long enough... I heard somewhere that AS5 takes like 5 days to completely cure for true temp tests.

 

[MarkHark]

As much mirror-finish as it may be, the fact remains, IF it is not touching the heatspreader homogeneously, THEN it is not perfectly flat. The center may be a bit elevated in relation to the borders, this seems to be a fabrication process limitation common to most heatsinks, even higher-quality ones. And that is why SOME people will sand their heatsinks no matter how well-polished they may be. And that MIGHT also be the reason why AMD has recommended the use of thermal pads OR higher-consistency thermal paste (i.e. Shin Etsu) instead of Arctic Silver, ever since the times of Tbred. Just a theory of mine, take it for what it's worth

 

[Lord Banshee]

I stand corrected