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To: ptanner who wrote (77872)	4/21/2002 8:07:45 PM
From: Bill Jackson	Read Replies (1) \| Respond to of 275872

PT, In heat sinks a lot depends on what you add to the plastic as filler. The thermal conductivity is inbetween that of the pure platic and pure additive. Some thermal pastes are 95% thermal compound(by weight) If you picked a very high thermal meterial, like diamond powder, you may be able to make a plastic heat sink that is better than copper, but it may cost more. Powdered tiny diamond grit is costly, but only small amounts are used. This example uses diamnd in copper, but there is no reason diamond in plastic cannot be used. Of course other thermal materials like copper powder used as copper in plastic would be cheaper. I am not sure of the relative merits of diamond/copper copper/plastic etc as I was unable to find any data or cist figures. Nicholas J. Colella, Howard L. Davidson, John A. Kerns, and Daniel M. Makowiecki Composite Material Having High Thermal Conductivity and Process for Fabricating Same U.S. Patent 5,783,316 July 21, 1998 A process for fabricating a composite material with high thermal conductivity for applications such as heat sinks or heat spreaders for high-density integrated circuits. The composite material produced by this process has a thermal conductivity between that of diamond and copper, consisting of coated diamond particles dispersed in a high-conductivity metal, such as copper. The composite material can be fabricated in small or relatively large sizes using inexpensive materials. The process uses a sputter-coating diamond powder with several elements (including a carbide-forming element and a brazable material), compacts them into a porous body, and infiltrates the porous body with a suitable braze material, such as copper-silver alloy, to produce a dense, diamond-copper composite material with a thermal conductivity comparable to synthetic diamond films at a fraction of the cost. The present invention can be used for integrated circuits, particularly copper-diamond heat sinks, and for copper-diamond composite material, such as that having high thermal conductivity for fabricating composite materials. Bill