General > General Technical Chat
When you need really good cooling: Mikrotik hAP ax3
(1/4) > >>
golden_labels:
A friend found this on a main board of a Microtik hAP ax3. Experts on applying thermal paste, this is your time! ;)
Nominal Animal:
What the actual fuck?  That image is the Monty Python dead parrot sketch of incorrect thermal paste use.

If you use enough paste to form a layer between the two surfaces the thermal performance is often worse than without any paste at all.
If the surfaces are not flat, use a thermal pad designed for the purpose; thermal paste is not that.
thm_w:
I'm thinking this IC is normally fitted and the paste is on the empty side of the board, to conduct to the aluminum. With the IC there it would not spray through.
Although it is a hilariously large amount as Norminal says.

Heres another photo where no paste is visible: https://www.reddit.com/r/mikrotik/comments/10i74a7/hap_ax3_disassembled_possible_expansion_slot/

There seems to be white thermal pad for the RAM visible also.
SiliconWizard:
I don't understand the picture.
Nominal Animal:

--- Quote from: thm_w on February 29, 2024, 12:11:35 am ---I'm thinking this IC is normally fitted and the paste is on the empty side of the board, to conduct to the aluminum.
--- End quote ---
Yep; and a thermal pad should be used there instead.  Similar cooling construction (from the opposite side of the board than the IC itself) is sometimes used for example for stepper driver ICs.  Some Trinamic ones for example allow a lower junction-to-heatsink thermal impedance that way (compared to heatsink on top of the IC).

Some SBCs like Odroid M1 are designed so that one entire side is covered by a heatsink (basically forming one side of an enclosure), with the most heat-generating ICs put on that side.  It works well, but any height differences must be taken up by different thickness thermal pads, not thermal paste.  Thermal paste is only effective if the heatsink surface is machined flat, the components the same height, and sufficient pressure (additional screws between components) is applied between the heatsink and the PCB.  Thermal pads are much more forgiving, although even their use must observe the limits of how much "give"/"crush" a specific pad allows before its properties are affected.

In this case, I think it is an one-off, an error by someone who thought they could replace a thermal pad they didn't have and didn't know the specific type or properties of, with gobbets of thermal paste.  "The parrot isn't dead, it's just resting."
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod