How is thermal paste made of silver?

DeltaTaco

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Feb 6, 2016
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So obviously silver is one of the most conductive elements out there, and its thermal conductivity makes it a perfect candidate for thermal paste. However, it is also very electrically conductive. Arctic Silver 5 is advertised as being "99.9 Pure Micronized Silver" but also "Non-electrically conductive" so how is this possible that it is almost pure silver but not conductive?
 

BFG-9000

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Thermal paste is mostly a grease carrier with some powdered solids in it. For AS5 the powder is ground up silver and it is considered very unlikely that the silver particles will ever perfectly line up to cause a short because of the very large amount of grease and tiny amount of solids. For the same reason it would be unlikely to make a reasonable capacitor because those are made of foil sheets with a very thin insulator in between, and the particles are all separate.

Unlikely isn't impossible though so keep it off pins and traces anyway!
 

Eximo

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I can't believe they advertise it that way...and then have a caveat directly beneath it.

"
Not Electrically Conductive:
Arctic Silver 5 was formulated to conduct heat, not electricity.
(While much safer than electrically conductive silver and copper greases, Arctic Silver 5 should be kept away from electrical traces, pins, and leads. While it is not electrically conductive, the compound is very slightly capacitive and could potentially cause problems if it bridges two close-proximity electrical paths.)
"

I assume the compound that isn't silver is non-conductive. But the silver itself will be, no way around that.
 

BFG-9000

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Thermal paste is mostly a grease carrier with some powdered solids in it. For AS5 the powder is ground up silver and it is considered very unlikely that the silver particles will ever perfectly line up to cause a short because of the very large amount of grease and tiny amount of solids. For the same reason it would be unlikely to make a reasonable capacitor because those are made of foil sheets with a very thin insulator in between, and the particles are all separate.

Unlikely isn't impossible though so keep it off pins and traces anyway!
 

Eximo

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Pretty much use Arctic MX-4 these days, also have various tubes of Thermaltake and Tuniq mid-range products, they all work well enough.

AS5 has been popular for a long time, but it hasn't been the best/cheapest option for quite some time. Silver is expensive.

http://overclocking.guide/thermal-paste-roundup-2015-47-products-tested-with-air-cooling-and-liquid-nitrogen-ln2/6/
 

BFG-9000

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I still like to use extra-thick pastes like AS5 on bare dies like GPUs and laptop chips, but anything with a heatspreader gets something thinner like Gelid GC-Extreme because the thick stuff would require too much pressure to squeeze out (and a thick layer of paste is bad for heat transfer).

AS5 was introduced in the heyday of Athlons and PIIs and still works fine for bare dies like those--which is what it was designed for.
 

Eximo

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Yep, it was my go to for Athlon XPs back in the day. But you were so far away from the contacts it was fairly safe with the zif sockets. LGA is kind of scary in that regard.

Thick pastes still work well for direct contact heat pipes, lot of grooves to fill.

But yes, with a very shiny and smooth interface some of the thinner pastes are best.

MX-4 is a nice middle ground, and is cheap.
 

DeltaTaco

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Feb 6, 2016
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So essentially AS5 is NOT actually "99.9% Silver" but made up of many things and the silver that is inside is pure, but in very small concentrations?
 

BFG-9000

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Yep, only the silver part is 99.9%. According to the MSDS it's not even the only powdered solid:
Silver (Metallic)
Boron Nitride (they do not specify if it's the grinding paste kind or the dry lubricant kind)
Zinc Oxide (the white stuff used in the cheapest silicone compound)
Aluminum Oxide (grinding paste)
Ester Oil Blend

I don't think the grinding paste is alarming because other thermal pastes use much harder diamond powder which is used to grind carbides.
 

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