RE: [SI-LIST] : multiwire experience?

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From: Willis, Ken (Ken.Willis@sycamorenet.com)
Date: Wed Jan 17 2001 - 05:02:50 PST


Hi Patrick,

I had looked at multiwire about 10 years back, and at the time
found for our netlist that the crossover point in terms of
cost was at 18 layers or so. Below 18 layers the traditional
PCB was more cost-effective, above 18 multiwire started to
make economic sense. We did have issues with supplier capacity
and second sourcing. I seem to remember that Hitachi had bought
up most of the production capability to use for HDTV boards or
something.

Here is some more stuff from memory. For electrical characteristics,
the impedance control was touted as capable of tighter tolerances
than regular PCBs because there was no etch width variation to
worry about. But I didn't really believe it because you would get
so many wire crossovers, which would capacitively load the line
and create impedance discontinuities. Same issue came to mind
for the delay control as well. Also, there was discussion then
about actually having a coax multiwire technology, but I don't
think they ever resolved how to ground the shield. That's all
I can remember.

Ken Willis
Sycamore Networks
(203) 294-8141
(203) 294-8080 fax
Ken.Willis@sycamorenet.com

-----Original Message-----
From: Zabinski, Patrick J. [mailto:zabinski.patrick@mayo.edu]
Sent: Monday, January 15, 2001 4:57 PM
To: si-list@silab.eng.sun.com
Subject: [SI-LIST] : multiwire experience?

On a particular project I'm working on, it has been proposed
that we use multiwire boards in place of traditional multilayer
printed circuit boards. Does anyone out there have experience,
good or bad, with multiwire you'd care to share? I'm interested
in any/all experience, including performance, crosstalk, design ease,
reliability, cost, etc....

Thanks,
Pat

-----
  Pat Zabinski Ph: 507-538-5499
  Mayo Foundation Fx: 507-284-9171
  200 First St SW Em: zabinski.patrick@mayo.edu
  Rochester, MN 55905 Wb: www.mayo.edu/sppdg/simulation.html

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