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To: K. M. Strickler who wrote (17226)	2/7/1998 2:52:00 PM
From: John Donahoe	Read Replies (1) \| Respond to of 24154

I'am not a IC designer. But I have designed circuits packaged on PC boards. The problem as I understand it is that copper conductors " layed down" on silicon is a more difficult process as compared to aluminum. So it becomes a cost thing. This is better understood by experts in materials processing. The use of copper offers the advantage of superior conductivity for a given geometry. And hence allows for smaller conductor geometries. These smaller geometries will allow lower voltages which inturn will lower switching heat losses. Capicitance stores energy. Since this stored energy is = 1/2CV^2 lowering voltage has a huge affect on heat loss. Anyway this is how it's viewed in the discrete world of transistor switching. Sort of a macro view of things. Capacitance and resistance are both affected by frequency. But when you do design you concentrate on the major contributors with small effects lost in the "noise". In MOSFET discrete design these effects are usually negligible. In Bipolar due to higher drive currents the "frequency component" in a resistance should probably be taken into account. I don't know what the relative significance of these frequency effects are in IC design. JD