Copper slug/embedded aluminum heatsinks...

[SunnyD]

I'm particularly interested in the heatsinks that have copper fused into the aluminum heatsink, like most video cards now have. They'll have a copper "slug" that's pretty much fused right into the aluminum. I would assume that it's something as simple as milling a receptacle for the copper, then pouring molten copper into the receptacle and allowing to cool.

But how to they account for different expansion coefficients? Or are the operating temperatures we're talking about with heat sinks low enough to not have to worry about different expansion rates?

 

[thilanliyan]

I don't know if it would be that simple. The melting point of copper is higher than Al so pouring molten copper onto Al might melt that as well.

Can you give me an example of what you're talking about? I don't know if I've ever seen one the way you describe it.

 

[Modelworks]

It is done by using copper slugs and very precise milling to bore the hole.
They heat the aluminum causing it to expand then insert the copper slug. It cools and its a perfect fit ! It is done the same way on automotive parts that are similar in design.

 

[SunnyD]

Originally posted by: Modelworks
It is done by using copper slugs and very precise milling to bore the hole.
They heat the aluminum causing it to expand then insert the copper slug. It cools and its a perfect fit ! It is done the same way on automotive parts that are similar in design.

Seems like a very process intensive and cost prohibitive method to do that.

 

[Modelworks]

Originally posted by: SunnyD

Originally posted by: Modelworks
It is done by using copper slugs and very precise milling to bore the hole.
They heat the aluminum causing it to expand then insert the copper slug. It cools and its a perfect fit ! It is done the same way on automotive parts that are similar in design.

Seems like a very process intensive and cost prohibitive method to do that.

Maybe so but that is how it is done.

Sometimes using frozen copper also for an even tighter fit.

 

[wwswimming]

Originally posted by: SunnyD

Originally posted by: Modelworks
It is done by using copper slugs and very precise milling to bore the hole.
They heat the aluminum causing it to expand then insert the copper slug. It cools and its a perfect fit ! It is done the same way on automotive parts that are similar in design.

Seems like a very process intensive and cost prohibitive method to do that.

it is, when you're doing one or setting up a pilot run of 1000.

if you're doing millions - like Intel's Core2Duo HSF's - piece of cake.

 

[SunnyD]

Originally posted by: wwswimming

Originally posted by: SunnyD

Originally posted by: Modelworks
It is done by using copper slugs and very precise milling to bore the hole.
They heat the aluminum causing it to expand then insert the copper slug. It cools and its a perfect fit ! It is done the same way on automotive parts that are similar in design.

Seems like a very process intensive and cost prohibitive method to do that.

it is, when you're doing one or setting up a pilot run of 1000.

if you're doing millions - like Intel's Core2Duo HSF's - piece of cake.

I read up on it, apparently they use induction heating on the heatsink. I suppose that would be a decent way of dealing with it from an efficiency standpoint. But it lead me to wonder - what about the air gap between the slug and the heatsink? I would think that would be a pretty big concern... unless the gap would be small enough to not worry about. I wonder if they put some sort of "interface medium" in there.

 

[Modelworks]

There really isn't much of a air gap. CNC machines can make the fit as close as .1 microns.

 

[Zepper]

Plus it's a pressure fit and copper is relatively soft - it will "flow" to fill any minute gaps.

.bh.