Re: [SI-LIST] : Decoupling capacitor selection & placemen
D. C. Sessions ([email protected])
Wed, 29 Oct 1997 08:21:35 -0700
[email protected] wrote:
>
> How does everyone feel about power/ground distributed capacitance?
>
> Zycon originally developed ZBC2000 - a thin FR4 (.002") power/ground
> core with a capacitance of ~500pf/sq in (usually 2 cores are used) -
> as a decoupling capacitor replacement or adjunct.
>
> HADCO and Polyclad have developed EmCap - a 0.004" Ceramic / FR4 epoxy
> power/ground core with 2750pf/sq in - as the next generation.
>
> I have been doing work to predict the ability of both these products
> to replace discrete capacitors in our customers boards and would like
> to hear some honest thoughts and feedback.
Right now the issue is cost. We need to keep in mind that the idea of
engineering is not usually to build the best <whatever> but to build a
<whatever> with adequate performance at minimum cost.
At some point declining costs and increasing performance demands (incl.
density) will force us to incorporate passives in the PWB substrate.
IMHO it's a race between power cores and resistive layers for
termination
to mainstream first. The other possibility is that people like me(!)
will incorporate termination onchip (as the Creator intended it) to
eliminate stubs and add capacitors onchip (on the RIHGT side of
bondwire inductance.)
--
D. C. Sessions
[email protected]