Thermal condution paste - none adhesive

I've just take apart an all-in-one PC and cleaned all the dust and crud out of the fan and radiator and it all works fine and quiet now.
BUT:

The cooling fan blows air into a radiator which houses some thermal conduction bars terminating in sprung flats screwed over the main processors. Clearly there is evidence of a gap-filling compound and I’d appreciate advice on what to use there if it needs doing again - something that will gap-fill but not glue or drip...

pgk

I assume you mean something like this, various types tested here.

Thor

That's the sorta thing looks like a paste rather tthan liquid for ham-fisted use...

pgk

If you are worried about ham-fisted use make sure you get a non-conductive thermal grease. The more expensive high performance "liquid metal" pastes are electrically conductive and if any gets on the pins you may say goodbye to the processor, and there is no need for them unless you are seriously overclocking.

Brian G

CPC list 2 which look suitable:

**LINK**

Stuart

I have used Arctic silver 5 for years, but there is some stiction when removing the heatsink, which is unavoidable.

Hi All,

Interesting thread for me as I have had to remove a large circuit board from a woodworking lathe to have it repaired.

When I undid the retaining screws and went to slide it out of the steel casing the bottom was covered in a thickish white paste.

The manual said this was to aid heat conduction from the alloy heat sink to the casing.

I believe there was a mention somewhere else in my research that this would be Zinc Oxide paste.

Would this be correct and is it the same Zinc Oxide as the old fashioned ointment of the same name?

Cheers, Martin

CPUs are normally mounted using silver conductive compound which is much less fussy about film thickness than straight silicone which is non-conductive and relies on a very thin, gap-filling application to do its job. AFAIK all the cpu manufacturers recommend/require it (silver).

That doesn't mean you put it (silver) on by the spoonful though. A thin wipe all over the CPU cover is enough to give a decent thermal connection to the heatsink (better than silicone).

Shorting out pins is greatly exaggerated. It's like a grease film. If you couldn't apply a thin film of that locally without getting it all over the pins you wouldn't be here.

Personally, if the original heatsink connection hasn't been broken, I'd leave it alone. It's most unlikely that you'll improve it. Cleaning out the crud that gathers around the fan and heatsink though with a vacuum cleaner is well worth doing from time to time, especially if you do any intensive processing (such as video editing). If you run a background cpu temperature-checker before and after clearing out the dirt you'll certainly notice a difference.

As described above in this specific case the radiator, coolant bars and coolant pads are inseparable such that the cleaning process required the pads to be lifted. I do own a conductive epoxy but avoided using that in case of future need to repeat the cleaning.
As it happens, I just re-assembled on the theory that the original material would be realigned if undisturbed and the machine currently runs whisper quiet. The fan noise had become increasingly annoying over the last several months in a 4year old machine and doubtless will require repeating at some future time when I shall arm myself with one of the paste materials from the suggestions above.
On previous PCs that I've had to clean the processor cooling systems were fans atop the processors which could be cleaned in situ so the arrangement here was new to me. The face of the radiator was 70% clogged with dust and sorted with a trip to the shed to blast an air-line through from the rear.
The type of thing can be seen at the video time point below, albeit that in my case there were three coolant bars going to 2 different processors.
https://youtu.be/CBdYzJOnfAo?t=547

pgk

.

It’s not immediately obvious from that short video clip, so I will just mention that those are ‘Heat Pipes’

**LINK** https://en.wikipedia.org/wiki/Heat_pipe

… and with a system like that, excellence of assembly is mandatory.

MichaelG.

.

https://support.lenovo.com/gb/en/solutions/pd027275-thermal-pipes-removal-and-installation-thinkpad-edge-e445

Edited By Michael Gilligan on 21/05/2022 06:25:03

Very educational this forum! Until this morning I assumed those Copper runs were just a simple metal conductor, used to transfer heat from a hot component such as a CPU across the circuit board to wherever it's mechanically convenient to mount a fan and radiator. Half right, now I know the pipe relies on latent heat and carries much more heat than a lump of Copper would.

Heat-sinks have always been a mystery to me: I know heat follows rules analogous to Ohms Law, but I've no idea how to design one. Big lump of Aluminium, with lots of fins, painted black, and don't assume it's earthed is the best I can do! How big and how many fins are just as wild guess.

Dave

Any thoughts on the Zinc Oxide paste?

Cheers, Martin

The original was almost certainly a silicone based 'heat sink' compound, something like this (which does contain zinc oxide).

https://cpc.farnell.com/servisol/200001000-25gm/heat-sink-compound-25g-tube/dp/SAHEATSINKCOMP

(Personally, I'd replace it with similar.)