Silver vs. Copper

Zeldak

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Nov 6, 2005
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Silver is a better thermal conductor than is copper. This is the physical basis for the use of silver-containing or silver-named TIM's.

A few years ago a number of people modded their CPU coolers to use a silver slug as the interface between CPU and heatsink. I believe there were even a few commercial coolers that used silver metal (in various thickness) as the interface material.

Does anyone have personal knowledge of or experience with the benefit of using heatsinks or coolers with silver metal as CPU contact? Is it at all useful in practice?
 
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dma0991

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No matter how good of a thermal conductor one material may be, if the benefit does not outweigh the cost, it becomes useless. We could make it out of diamond (IC Diamond 24), but would anybody be willing to bear the exponential increase in cost for miniscule improvement?
 

Zeldak

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Thank you for the response. Another way of phrasing my question: did silver, superior physical properties notwithstanding, ever show more than miniscule benefit as a heatsink component? Market review would imply that it didn't.

I suppose that the limitation may have been transmission of heat from the silver insert to the remainder of the heatsink material. I have no idea if anyone actually went so far as to fabricate an entire heatsink of silver.
 

BonzaiDuck

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Jun 30, 2004
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There are some silver water blocks.

Yes, there were . . . . and my more recent searches of the last couple months doesn't show any -- I couldn't find them.

I played around with the issue or promise of better thermal conduction with silver back in '07. Somebody gave me a newly-minted silver dollar -- Now, it's a "silver slug." But I still have it. The only way this could be beneficial would be to shape or stamp it as an exact replacement for a heatspreader, and if you're going to remove the heatspreader anyway, you'll be tempted to make a "bare die" application.

So the most useful example I'd seen was a silver water-block. You can't do much with your silver slug if it just adds to the intermediate thermal interfaces -- your temperatures will only be higher. If you could somehow plate a heatsink base with it, there might be marginal benefit, but the only ultimate gain of any significance would be to replace the entire heatsink base.

The point about cost is salient. They're not going to manufacture something with a precious metal if the target customer-base is sparse. To me, the addition in cost for either a water-block or heatsink base is worth it; other people aren't likely to think so.

On the remark about "nano-diamond" and the IC Diamond product. Synthetic diamond isn't all that expensive, and what's better -- used diamond paste is re-useable. You get fewer "applications" in a tube, but it only takes one. Doesn't pump out; doesn't degrade; doesn't require "curing."
 

Blain

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Oct 9, 1999
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Silver water blocks may be a little better than copper in heat transfer.
But after a few weeks of gunk (technical term), building up and coating the internal surfaces, silver doesn't really shine as "better" given the cost.

I laugh out loud when "silver" is brought up as a better alternative in cooling than copper.
Read through some of these "help me build" threads...
People that are building with junk PS because the wattage is "as good", but the price is much cheaper.
Some how I don't see these people saying... "I must have silver for cooling".

The difference between silver and copper thermal conductivity isn't night and day, at all...Silver barely pulls ahead of copper.
 
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Zeldak

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Silver's thermal (and electrical) conductivity is the highest of all metallic elements--roughly 20% better than copper. I didn't know there were ever silver water blocks--it would be fascinating to play with one. Plating wouldn't be near the advantage of solid silver, and it wouldn't really require that much of it for a water block. The interior gunk is the same whatever the block material.
Like BonzaiDuck, I had a nice silver slug ready to try a few years ago, but in my case a nasty car crash and injury definitely put that project on hold. As BD says, the problem with slugs is the interface with whatever else the heatsink is made of.
For a hard core overclocker stopping short of liquid nitrogen or chilled glycerin immersion, a silver water block would have to represent a measurable advantage. But of what percentage . . .
Would BonzaiDuck be running just as cool at 5Ghz with silver as he is now at 4.7 on copper? My bet is yes. I would personally pitch in at least $50 for him to find out!
 

LtGoonRush

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The thermal conductivity of silver is actually only about 5% better than copper, so there isn't likely to be a measurable performance difference and certainly not enough to justify the costs. The thermal conductivity of metal actually isn't super important to the performance of modern heatsinks because they use vapor-phase heatpipes to carry heat from the CPU to a massive aluminum radiator. Because the heatpipes are transporting the heat rather than it simply conducting through metal, there isn't much performance improvement from replacing the aluminum radiator plates with copper even though it has much higher conductivity.

Similarly, I don't think most heatsinks are currently limited by their ability to spread heat from the CPU through their base to multiple heatpipes, as evidenced by the fact that direct-touch heatsinks with no heat spreader at all (aside from what's on the CPU) aren't markedly worse than others. If you really needed a heatsink base that did a better job of spreading heat then I think using a vapor chamber (basically a flat heatpipe that spreads heat over an area rather than conducting it down a tube) would get you MUCH better performance than switching from copper to silver. This is what videocard heatsinks do where spreading heat across the base IS important.
 

videogames101

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Aug 24, 2005
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Copper: $3.0430 per pound

Silver: $19.95 per ounce

5%? haha nope

not to mention the fact that silver tarnishes extremely easily, and copper is much more resistant to corrosion
 

BonzaiDuck

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Copper: $3.0430 per pound

Silver: $19.95 per ounce

5%? haha nope

not to mention the fact that silver tarnishes extremely easily, and copper is much more resistant to corrosion

There you have it. Now that I remember, Silver pulled ahead of copper in thermal conductivity by 25%, Diamond pulls ahead of both by between 400 to 500%, whichever base you use to compare it.

So in this comparison and the magnitudes, consider how Noctua's copper-diamond composite offers 25% better thermal conductivity with their forthcoming D15. How that translates into centigrade performance, I suppose we'll have to wait and see. . . .

But that's interesting, for cost-accounting speculations. It suggests that both the nano-diamond ingredient and the process of making the composite base costs less than fabricating and using silver for a heatsink base, and the difference must be significant or Noctua wouldn't bother with it -- whatever MSRP they propose for the D15.

On Copper and corrosion, however, what videogames suggests may be true, but there's also a reason why the IHS and all but direct-touch heatsink bases are plated with nickel. Nickel is worse for thermal conductivity by an order of degree equal to the difference between copper and silver.

PS If Zeldak says Cu vs Ag is 20%, then I stand corrected by 5% -- but that was off the top of my head. Noctua quoted 25% for their base, and Diamond is so far "up there" that even my faulty memory would yield a degree of accuracy there . . .
 
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Zeldak

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BonzaiDuck summarizes the relevant issues very well. It's interesting to me that thermal conductivity data are variously reported. One credible source cites an Ag-Cu difference as almost 20%, while another (probably more credible) source cites only about 5%. Definitely confusing.


I also found an interesting, though rather outlandish, discussion of the matter on a site dedicated to overclocking. One of the posters there reported the "buttery soft" hardness of silver. Metallic sodium could be described as "buttery soft," but not silver. Silver is plenty hard to fabricate a heat sink or water block.


I'm still down to financially contribute should BonzaiDuck acquire a silver water block. I think it would be a really fun thing to try, even if it eventually showed trivial benefit over copper.
 

MagnusTheBrewer

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Jun 19, 2004
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Answer me this though, why does cost benefit analysis apply to everything but CPU, GPU and, "quietness? "
 

LtGoonRush

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I also found an interesting, though rather outlandish, discussion of the matter on a site dedicated to overclocking. One of the posters there reported the "buttery soft" hardness of silver. Metallic sodium could be described as "buttery soft," but not silver. Silver is plenty hard to fabricate a heat sink or water block.
While not truly "buttery soft" like metallic sodium, silver is still a very soft metal (on par with gold) and is typically alloyed with copper to produce a metal that is strong enough to be functional. My concern would be the base of the heat plate denting around the CPU/IHS, though that would actually improve thermal contact if used with only a single CPU. Copper-based coolers can dent under sufficient contact pressure, so I would think that even sterling silver (7.5% copper) may not be strong enough.
 

Blain

Lifer
Oct 9, 1999
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Do a Google search on the whole silver/copper issue when it comes to cooling.
Really, it's been done to death for years now.
Nothing new can be added to what's already out there.
 

Zeldak

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Nov 6, 2005
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I'm afraid Blain is right. Still fun to think about.

Still, it looks more like it's been talked to death rather than tried so much.
And a lot of the talk is questionably informed despite impressively authoritative attitude.



Please try not to double post... go back and edit original post if you wish to add more comments to the original post.

Cases and Cooling Moderator Aigo
 
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BonzaiDuck

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Still, it looks more like it's been talked to death rather than tried so much.
And a lot of the talk is questionably informed despite impressively authoritative attitude.

I'd have to look up my own sources, but the comparison between Nickel, Copper, Silver, Gold and Diamond had been printed in a table for general "scientific purposes." It was simply the heat conductivity of each -- probably in Watts-per-Centigrade. My understanding of it -- never that thorough -- was that thermal conductivity is the inverse of thermal resistance. The latter is almost always in units of C-degrees/watts or C/W.

Essentially, that's the way I remember it.

It may be that what you or someone had seen as a 5% difference was simply the improvement in temperature -- I can't rightly say.
 

Zeldak

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The thermal conductivity of silver is actually only about 5% better than copper, so there isn't likely to be a measurable performance difference and certainly not enough to justify the costs. The thermal conductivity of metal actually isn't super important to the performance of modern heatsinks because they use vapor-phase heatpipes to carry heat from the CPU to a massive aluminum radiator. Because the heatpipes are transporting the heat rather than it simply conducting through metal, there isn't much performance improvement from replacing the aluminum radiator plates with copper even though it has much higher conductivity.

Similarly, I don't think most heatsinks are currently limited by their ability to spread heat from the CPU through their base to multiple heatpipes, as evidenced by the fact that direct-touch heatsinks with no heat spreader at all (aside from what's on the CPU) aren't markedly worse than others. If you really needed a heatsink base that did a better job of spreading heat then I think using a vapor chamber (basically a flat heatpipe that spreads heat over an area rather than conducting it down a tube) would get you MUCH better performance than switching from copper to silver. This is what videocard heatsinks do where spreading heat across the base IS important.

I didn't know that about heat pipes. What do they contain as a vapor-phase medium?
 

imagoon

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Feb 19, 2003
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While silver is 5% better than copper at heat conductivity, my unresearched thought would be that a silver slug in copper would lose a decent chunk of that gain at the metal junctions. I mean 2 metals with 2 expansion rates means there would be gaps of some sort at the metal junctions. Maybe if they plated the silver on but I am not sure if they would get it thick enough to make it matter.
 

aigomorla

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While silver is 5% better than copper at heat conductivity, my unresearched thought would be that a silver slug in copper would lose a decent chunk of that gain at the metal junctions. I mean 2 metals with 2 expansion rates means there would be gaps of some sort at the metal junctions. Maybe if they plated the silver on but I am not sure if they would get it thick enough to make it matter.

no because your stuck at the limited element.

Lets assume this..

You have a 18Wheeler truck, and a Uhal truck.

The 18wheeler truck can deliver a full package of whatever, however when the Uhal truck can not move the same capacity in 1 trip unless it was to drive a lot faster, hence the potential of transfer will be limited at the Uhal with very little gain.

The same can be said for the other way around.
This however is then known as holding potential.
The uhal truck can bring packages to the 18wheeler, but will never saturate it or fill it up with 1 trip, the holding potential will be greater at the intial end, but when the system reaches equilibrium, you will again be limited by the lower potential as it exists the system.
 
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imagoon

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Feb 19, 2003
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no because your stuck at the limited element.

Lets assume this..

You have a 18Wheeler truck, and a Uhal truck.

The 18wheeler truck can deliver a full package of whatever, however when the Uhal truck can not move the same capacity in 1 trip unless it was to drive a lot faster, hence the potential of transfer will be limited at the Uhal with very little gain.

The same can be said for the other way around.
This however is then known as holding potential.
The uhal truck can bring packages to the 18wheeler, but will never saturate it or fill it up with 1 trip, the holding potential will be greater at the intial end, but when the system reaches equilibrium, you will again be limited by the lower potential as it exists the system.

I'm not quite sure your analogy makes any sense....
 

BonzaiDuck

Lifer
Jun 30, 2004
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I'm not quite sure your analogy makes any sense....

First, let me correct your statement that Ag shows a 5% edge over Cu in thermal conductivity. The table of metals and their thermal conductivities show it to be more like 20%. How that translates into actual cooling performance -- which might be a piddly 5% after all -- hangs on Aigo's analog.

His point is simply this.

The heatpipe cooler consists of several "parts" or stages in heat removal from the IHS to the heatsink fins. In between that, there's the TIM and the heatpipes. If the heatsink base has an advantage of 20% over the traditional solid copper, it won't matter if heat transfer is bottlenecked by the same heatpipes and fins if it had been the heatsink base which had previously been the bottleneck with pure copper. In other words, if the heatsink base had prevented the pipe and fin design from achieving its full potential at heat removal, you're likely to see some improvement if only the heatsink base had been replaced with something better.

This thinking also explains why you can't just sandwich a wafer of silver between the IHS and a heatsink base to expect improvement, and why doing so will simply degrade cooling significantly. The bottleneck there is still the IHS (nickel-plated copper) and now two layers of TIM. The heat still must travel through the silver, the next layer of TIM, and then the heat removal is still determined by the copper heatsink base.
 

imagoon

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Feb 19, 2003
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First, let me correct your statement that Ag shows a 5% edge over Cu in thermal conductivity. The table of metals and their thermal conductivities show it to be more like 20%. How that translates into actual cooling performance -- which might be a piddly 5% after all -- hangs on Aigo's analog.

His point is simply this.

The heatpipe cooler consists of several "parts" or stages in heat removal from the IHS to the heatsink fins. In between that, there's the TIM and the heatpipes. If the heatsink base has an advantage of 20% over the traditional solid copper, it won't matter if heat transfer is bottlenecked by the same heatpipes and fins if it had been the heatsink base which had previously been the bottleneck with pure copper. In other words, if the heatsink base had prevented the pipe and fin design from achieving its full potential at heat removal, you're likely to see some improvement if only the heatsink base had been replaced with something better.

This thinking also explains why you can't just sandwich a wafer of silver between the IHS and a heatsink base to expect improvement, and why doing so will simply degrade cooling significantly. The bottleneck there is still the IHS (nickel-plated copper) and now two layers of TIM. The heat still must travel through the silver, the next layer of TIM, and then the heat removal is still determined by the copper heatsink base.

Ah since I wasn't talking about heat pipes, that would make sense why his comment made zero sense. My point was if put a silver slug inside a copper sink, I would think the silver to copper junction might be inefficient enough to over come any gains from the silver. Basically your comment: "This thinking also explains why you can't just sandwich a wafer of silver between the IHS and a heatsink base to expect improvement" Is what I was suggesting that I thought would happen but I hadn't researched it.