RE: [SI-LIST] : multiwire experience?

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From: Knighten, Jim L (JK100005@exchange.SanDiegoCA.NCR.COM)
Date: Mon Jan 15 2001 - 16:10:19 PST


Pat,

Discrete Wire Technology is the more generic term apparently in use now.
The term "Multiwire" may be specific to a vendor.

While this technology is expensive and not in widespread use, there is
increasing interest in this technology for PCBs containing high densities of
multi-gigabit/s signals.

Work in academia is ongoing in examining the signal integrity aspects of
features of this construction. I listened to a paper given this past fall
at a symposium on EMI given in Belgium. This work was gone by a group from
Italy and is obviously work in progress. I can put you in contact with
them, if you would like.

Jim Knighten
________________________________________________________
Dr. Jim Knighten e-mail: jim.knighten@ncr.com
<jim.knighten@ncr.com>
Technical Consultant - Design
NCR
17095 Via del Campo
San Diego, CA 92127 http://www.ncr.com <http://www.ncr.com>
Tel: 858-485-2537
Fax: 858-485-3788

                -----Original Message-----
                From: Thomas Jackson [mailto:tjackson@fmi.fujitsu.com]
                Sent: Monday, January 15, 2001 2:41 PM
                To: 'Zabinski, Patrick J.'; si-list@silab.eng.sun.com
                Subject: RE: [SI-LIST] : multiwire experience?

                 << File: Thomas Jackson.vcf >> Multiwire is a proprietary
technology. There is a very short list of places
                to get it done, so I don't think it is very cheap.

                It was favored when making PCBs with more than two layers
was prohibitively
                expensive.

                It has fallen from favor for a number of reasons. First,
the technology
                assumes that an insulated wire can be accurately placed in a
layer of liquid
                epoxy such that, later on, after the epoxy hardens, a CNC
drill can drill
                through that wire and make a through hole in the substrate.
Next
                assumption: Plating that hole will form a good electrical
contact with both
                of the sheared ends of that wire.

                Second, electrically, I have some reservations about its
signal performance.
                I don't see how each wire can be a uniform distance from a
power or ground
                plane over its entire length, so there must be impedance
variations. The
                Multiwire boards I have seen have had only one pair of power
and ground
                planes. Therefore, everything is microstrip at various
heights above the
                plane.

                At my previous employer, a defense contractor, they were
redesigning
                Multiwire boards for old systems into PCBs because they were
more
                supportable.

                While Multiwire had its day in the sun, I don't think I
would go that way
                today with the current cost and performance of PCBs.

                Tom

                Thomas L. Jackson, P.E.
                Staff VLSI Design Engineer
                Network Access Development
                Systems Solutions Group
                FUJITSU MICROELECTRONICS, INC.
                3545 North First Street
                San Jose, CA 95134-1804
                telephone: (408) 922-9574
                facsimile: (408) 922-9618
                http://www.fujitsumicro.com

                -----Original Message-----
                From: Zabinski, Patrick J.
[mailto:zabinski.patrick@mayo.edu]
                Sent: Monday, January 15, 2001 1:57 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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