Thermal paste

[hamdi.tn]

Hi, i just bought a gray thermal paste from a local electronic shop, first time i saw it. what's the difference between a gray one and the white one. i googled it and some talking about 'metal' or silver paste. is this supposed to be better thermal conductive paste.
if this has any meaning it's a HC-151 thermal paste.

i can't see the "general chat" category on the main page of the forum, was it removed

edit : am an idiot, the general category was not collapsed 

[Philfreeze]

https://www.eevblog.com/forum/chat/
Nah general chat is still here. You just have to scroll down to general (First is Electronics, then products and then general).

As far as I know the white stuff is Silicone thermal paste and the grey metal thermal paste (mostly alluminium nitrid or silver) but I am not sure.

[RGB255_0_0]

Highly unlikely to be metallic if it's cheap. Metal-based ones would be Coollaboritory, Arctic Silver (not Ceramique) and other top brands may have metallic-based products.

Unless you're cooling a high thermal load you're probably fine.

What is it you're cooling?

[hayatepilot]

Don't forget to buy thermal future too!! 

Sorry, couldn't resist.
White thermal paste contains usually only silicone compounds. They are very cheap but they don't conduct the heat very well.
Better pastes contain metal oxides and other compounds: https://en.wikipedia.org/wiki/Thermal_grease

Those yield the gray colour. But the colour alone doesn't say anything about the thermal conductivity. Only the datasheet does. 

Greetings

[Philfreeze]

Better pastes contain metal oxides and other compounds:

Those yield the gray colour.

Does this mean I was right?
White = silicone based
grey = with metal
Of course this will only apply 99% of the time because someone wants to sell its silicone based paste as metal based one thus using some color....

[hamdi.tn]

Don't forget to buy thermal future too!! 
Sorry, couldn't resist.

you totally right not to resist 
oh man !   

Better pastes contain metal oxides and other compounds:

Those yield the gray colour.

Does this mean I was right?
White = silicone based
grey = with metal
Of course this will only apply 99% of the time because someone wants to sell its silicone based paste as metal based one thus using some color....

you right and this one is one of those Chinese one , a gray silicone one.

White thermal paste contains usually only silicone compounds. They are very cheap but they don't conduct the heat very well.
Better pastes contain metal oxides and other compounds

Thanks 

[MrSlack]

+1 for arctic silver. Bought a big tube of that about 12 years ago and it's still going strong in everything I've put it in.

[Mephitus]

I have been a big fan of the arctic silver 5 for well over a decade in building and computers. For general purpose cooling (up to about 125w) I highly recommend it. For 50w or below, the cheap thermal greases are usually more than adequate. Anything 150w or higher, especially cooling critical components like CPU's, I would recommend looking into a ceramic based compound (like Céramique). If you are an extremist looking to cool a component in the most extreme way, you can even find diamond particle based compounds like the Innovation brand "7 carat". Hell, some people have made their own version of this: hackaday.com/2009/08/03/diamond-thermal-paste/

If you are wondering about any particular brand or compound, just google the name to find a ton of places that do a side-by-side shootout between it and many others. Working in IT for the last decade I have always used Arctic Silver 5 for all of my standard system builds with confidence and no issues (if you do it correctly). For oddly placed components without a way to properly mount a good heatsink, I have used the ceramic based thermal glue Arctic brand "Alumina".

[mstoer]

I found this page (http://www.dansdata.com/goop.htm) some time ago when looking up comparisons for thermal paste.  Apparently toothpaste works too!

[alsetalokin4017]

No mention of _electrical_ conductivity differences?

[RGB255_0_0]

Metal-based ones are going to be conductive. Certainly people killed CPUs back in the non-heatspreader days (Athlon/Duron).

But you also have to take into other considerations with thermal paste. "Diamond" ones can scratch/are abrasive; others may well not perform in the right conditions (extreme cold); some go hard.

I won't go into which one is "best" but I'm a bit of a fan of Gelid Extreme. Certainly keeps my 5820K cooler than AS5 did by about 2C.

[hamdi.tn]

I have been a big fan of the arctic silver 5 for well over a decade in building and computers. For general purpose cooling (up to about 125w) I highly recommend it. For 50w or below, the cheap thermal greases are usually more than adequate. Anything 150w or higher, especially cooling critical components like CPU's, I would recommend looking into a ceramic based compound (like Céramique). If you are an extremist looking to cool a component in the most extreme way, you can even find diamond particle based compounds like the Innovation brand "7 carat". Hell, some people have made their own version of this: hackaday.com/2009/08/03/diamond-thermal-paste/

If you are wondering about any particular brand or compound, just google the name to find a ton of places that do a side-by-side shootout between it and many others. Working in IT for the last decade I have always used Arctic Silver 5 for all of my standard system builds with confidence and no issues (if you do it correctly). For oddly placed components without a way to properly mount a good heatsink, I have used the ceramic based thermal glue Arctic brand "Alumina".

thanks everyone for your answers and suggestions, am using it on a triac that i replaced when repairing an oven, nothing too serious.

[EEMarc]

Metal-based ones are going to be conductive. Certainly people killed CPUs back in the non-heatspreader days (Athlon/Duron).

Arctic Silver 5 is claimed to not be conductive, but slightly capacitive. From what I've heard, the knockoffs color the paste so they look like Arctic Silver but not actually perform like it.

Better safe than sorry, especially when dealing with high dollar equipment.

[Chalcogenide]

I have had very good experience with Arctic Ceramique 2. It's cheaper than the Silver, is ceramic-based, so non conductive nor capacitive. It's thick and even thicker when cold, but I have had zero problems with it (and in the 2+ years I have had the same 25g tube, it has not separated at all).

[Mephitus]

thanks everyone for your answers and suggestions, am using it on a triac that i replaced when repairing an oven, nothing too serious.

If the triac is attached to a heatsink or case with a screw, like pictured below, then a thermal pad or mica shim with silicone based thermal grease should be just fine.

[hamdi.tn]

it's attached to the chassis of the oven, not with screw or any thing, just a piece of metal applying pressure on the triac case against the chassis. so yeah this silicone thermal grease is enough for the task.

[hayatepilot]

The cheap silicone based grease is enough for most applicacions (Transistors, MOSFETs, rectifiers...).
You pretty much only need high performance pastes if you have to cool a CPU or GPU which dissipate >50W on like 200mm².

Everything is better than no paste at all. 

Greetings

[Keridos]

On unnamed ones you might want to check conductivity with a Multimeter. If electric isolation is required use a thermal pad between the triac and the heatsink. That one can be quite important because in my experience some transistors etc. can have weird connections to the heatsink.

[Brumby]

Don't forget cardinal rule No 1 in applying thermal paste: Less is best!

Yes, you need to use as much as is required to cover the contact area, but as thinly as possible.  You want the metal surfaces as close as possible to each other AND have no insulating pockets of air.  That's all the thermal pastes do - displace the air.

ALL thermal pastes are not particularly good conductors of heat - but they are far better than air.