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Technology Stocks : Advanced Micro Devices - Moderated (AMD)
AMD 259.65+2.3%Jan 23 9:30 AM EST
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To: Mani1 who wrote (77912)4/22/2002 3:00:11 AM
From: tcmayRead Replies (3) of 275872
 
"My point is that the addition of the heat slug into the total package ads to the total thermal resistance. If you look at the current Athlon package, you see the bare die is showing. Future plan for AMD is to glue in a lid (or slug) on top of that die. This lid protects the die, but thermaly it does not help since it adds another layer of thermal resistance."

If part of the die is showing, then they certainly _should_ increase the area of the IHS/slug.

An air gap (or vacuum, or resin) is certainly _worse_ in terms of thermal resistance.

Here's what you wrote earlier:

"Yes, larger contact area is not really an advantage. Because you are effectively adding a new resister in your thermal circuit."

This sure looks like you are saying "larger contact area" is not really an advantage. It is.

BTW, it is _not_ necessarily the case that the best thermal contact (lowest junction-to-case thermal resistance) is achieved by placing the die in direct contact with the leadframe or case.

A high thermal conductivity layer with a larger area than the die (e.g., like the IHS and slug in dnp.co.jp the heat transfer in exactly the way I described earlier.

Heat transfer to the IHS or slug is efficient. The IHS or slug can transfer over a much larger surface area to a lower thermal conductivity material. Net result? Overall increased conductivity, even though the heat spreader has been placed between the die and the case/package/etc.

Hence the term "heat spreader."

--Tim May
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