[SI-LIST] Re: Guard Traces
- From: Colin D Bennett <colin@xxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Mon, 12 Mar 2012 11:16:31 -0700
On Mon, 12 Mar 2012 17:37:19 +0000
Eric Steimle <eric.steimle@xxxxxxxxxx> wrote:
> All this talk about low cost consumer boards brings back
> memories, before I switched to networking I did a lot of consumer
> product boards that were limited to two layers. We even did
> DDR2 and USB HS on 2 layer boards, although I wouldn't advise
> anyone to try it ;) Our tool vendors just threw up their hands
> and said good luck when we asked if they could simulate the
> return currents (except maybe some expensive 3D solvers and if
> you don't have money for 4 layer boards... who's going to buy you
> that).
>
> Eventually we found, at least at our volumes (1M+/year) that four
> layer boards really weren't all that much more expensive than a
> two layer. Maybe $0.25 - $0.50 more depending on area, and most
> of our customers with better engineering departments switched
> over as speeds went up. Granted that translates into $250k -
> $500k in revenue, but you also have to consider how much more
> engineering dollars have to be spent to make those two layer
> boards work, how much more trouble we had getting through FCC,
> and how much later the products showed up to market because of
> all that extra effort.
Hi Eric,
Thanks for the response. You do bring up a good point: all the
engineering effort required and potentially EMI/EMC approval issues
are much higher for a high speed two-layer design... it really
might ultimately make business sense to go with a more robust
four-layer board even for such cost-sensitive products. I will
certainly try not rule out multi-layers boards too quickly for these
designs.
Regards,
Colin
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