Quote:
Originally posted by myv65
Hey gmat,
The conductivity differential between silver and copper hardly makes for much improvement in spreading of the heat. At 300K, silver's conductivity is 429 W/m-K while copper's is 401. Electroplating also isn't real effective for depositing significant material thickness. Based on this, I wouldn't see a sizeable gain to be had in heat spreading via silver electroplating.
If you want to go the silver route for spreading, you'd have better results from a slug (few mm thickness) similar to the copper insert currently used on some air heat sinks. Even then, with less than a 10% gain in conductivity it would be a pretty minor improvement.
No question that it would be an improvement, just a very, very small one.
I think you'd see far more (temperature) variation simply in installation technique from person to person and in mounting style from block to block.
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Well, that's still a 7% improvement, but you're right, it probably wouldn't do anything that couldn't be compensated with a higher flow rate.
Still, although I believe that the silver plating has a few advantages:
1-although the original surface would still need to be lapped, the plated surface might have a finish that Arctic Silver can fill up better. I was hoping that the plated surface wouldn't need to be lapped, and if I send it out, I'd have to specify that they should not attempt to polish it, because I don't want "buffing compound" as the interface material between the block and the CPU core.
2-I thought it might help to transfer heat from the core to the copper part of the block, so I guess I'm saying that it might offer less resistance, but as gmat pointed out, it might have to be calculated, but I was thinking more simply in terms of using silver to act as a transition surface, as the material to be filled by the Arctic Silver, so I don't think that it needs to be calculated, it just needs to cover 100% of the bottom surface, with enough thickness to make sure that any irregularities are made entirely of silver.
Also, since the block is still a copper block, the rate of heat transfer would be limited to that of the copper.
So, the theory still stands:
1-get a copper block.
2-lap it as much as possible.
then, depending on how well lapped it is, will determine the required thickness of the plating.
What would be the size (max depth) of the irregularities, if the block was lapped to 600? 800? 1000? 1200? 1500? 2000? (assuming a circular pattern, for lapping)
3-Have the block's bottom plated to the thickness (above)
Alternatively, we could pick a thickness that would cover just about everything.
4-Get it back, and lap it again, with the finest of the finest of sandpapers, using water as a lubricant.
How does that sound?
BTW, the Arctic Silver website kindly points out that typically, only 1% of a surface comes in contact with another one. 99% is contacted through the paste. (true?)