Thermal compound question

[rumpelfilter]

Hi everybody, I have just entered the magical world of midibox by buying a sammichSID kit from Wilba. I've assembled kits before (APC, Shruti-1) and do some occasional bending on toys, so i think I can handle this one, but there is one thing I'm not really sure about: Wilba mentiones in the guide not to use conductive thermal compound... the problem is, how do I know which compound is conductive and which one isn't. I have some tubes at home f(CPU heatsink compund) which is labeled to be on Metal-oxyd basis. I've checked Reichelt.de (where I usually buy stuff and the thermal compound there, is the same metal oxyd one)... so the question is: will the stuff I have at home all right for the Sammich? The next question is, how exactly is the compound supposed to short the regulator? by bridging the ground with some other contact? Just to know so I know what to take care of... thanks a lot! Hannes

[Echopraxia]

I had the same question. If your careful you can use a conductive compound. You have to be VERY CAREFUL when applying it to not touch any leads of the regulators (or any thing else for that matter) which are very close to the heatsinks where the compound will be. I used as little as possible and my sammich works fine. Take the extra time to make sure your compound isn't all over the place. Wilba did not want everybody to try using conductive compounds because EXTRA CARE in the application is required.

echo

[Wilba]

AFAIK all the "silicone"-based thermal compount/heat transfer grease/white goo, etc. is non-conductive. It's the cheap crap that people stick between heatsinks and hot things all the time. If people want to use the same stuff they used between their CPU and the fancy CPU fan, there's nothing wrong with that, just make sure you don't short the pins of the regulators... and yes, this could be bridging ground (middle pin) with either the input or output of the voltage regulator (outer pins).

I think it was in the first batch of kits that someone had a lot of trouble when they got arctic silver all over that section of the PCB, which is why I now recommend people avoid using it.

[rumpelfilter]

thanks for the info! I'll use the one I have, I think as always with thermal compound, the base rule is "use as little as possible" if you use too much of it it's bad for thermal conduciveness as well...