Epoxy for CPU Cooling

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Is epoxy better than thermal grease?–Joe

SUMMARY: Using Arctic Silver Epoxy as heatsink grease transfers heat better but at a high price – CPU immobility.

Let me say something off the bat:

I DO NOT RECOMMEND DOING THIS AT ALL!

Gluing a heatsink to your CPU may result in damage to your CPU and possibly motherboard when you try to remove the heatsink. Make no bones about it – this is a radical move.

Having said all that, it came to my attention that some folks are gluing heatsinks to CPUs using Arctic Silver epoxy, claiming better performance than regular Arctic Silver. Being of inquiring mind, I decided to give it a test.

THE TEST

To test this out, I used a Duron 650 that I had lying around. I mounted it on an ABIT KT7, running it at 900 MHz, 1.91 volts, 58 watts, cooled with a Vantec CCK-6027D using a YS Tech 40 cfm fan. I first ran it with Arctic Silver for one hour with Prime 95 and then recorded temps. I then cleaned the heatsink and CPU with acetone and applied a thin layer of Arctic Silver epoxy to the CPU and mounted the Vantec to it. I waited an hour for it to set and ran Prime 95 again for one hour and recorded temps.

TEST RESULTS

Grease

CPU Case Temp

Ambient Temp

Delta

C/W

MBM Temp

CPU Back Temp

Arctic Silver

38.6 C

22.7 C

15.9

0.27

37 C

39.1 C

Arctic Silver EPOXY

38.1 C

23.1 C

15.0

0.26

37 C

39.0 C

Delta = CPU temp – Ambient Temp
C/W = Delta / CPU Watts

Interpreting C/W: For every watt the CPU radiates, the heatsink will cool the core by the (C/W x watts) plus ambient temp. For example, at an ambient temp of 25 C, a C/W of 0.25 with a CPU radiating 50 watts means that the CPU temp will be 50 x 0.25 = 12.5 C over ambient temp, or 37.5 C. The lower the C/W, the better.

There is a difference, although whether you think this is enough to justify a more-or-less permanent arrangement is up to you. I was able to get the heatsink off the CPU by twisting it; if it does not come off, you can’t get the heatsink/CPU off the socket (the lever arm has no room).

CONCLUSIONS

The gains I found are minimal and I believe do not justify so radical a move.

However, there is one application where I think it might make sense: If you a running a peltier with a coldplate, then using Arctic Silver Epoxy to bond the coldplate to the peltier could work well. Peltiers perform best when the coldplate is under high pressure to the peltier; bonding both with the epoxy while applying high pressure might make a performance difference.

What I don’t know is if the epoxy bond will survive the extreme temp cycling, so if you try this, drop a note on how it goes.

Email Joe

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