Re: 2 layer Versus 4 layer boards

From: Ian Stirling (root_at_mauve.demon.co.uk)
Date: 08/07/04 

Date: 07 Aug 2004 18:09:33 GMT

Keith <krw@att.bizzzz> wrote:
> On Sat, 07 Aug 2004 12:54:52 -0700, Rob wrote:
>
>> What are the benefits of 4 layer over a 2 layer (plain old double sided)
>> PCB?
>> We are reworking some old product designs and one line of thought is to go
>> to 4 layer.
>
> Usually four-layer boards are laid out 2P(ower)-2S(ignal) with power
> on the inner planes (there is an argument for them on the outer also.
> Using planes reduces the power impedance making lower noise easier. At
> high speeds this is a requirement (I wouldn't think of using signal wiring
> as power distribution). Power planes also allow a controlled trace

It depends how much work you'r willing to put into the design.
I had one PCI soundcard, 2 layer, that beat the chipset manufacturers
S/N figures for their 6 layer reference design.

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