[SI-LIST] Re: AW: Glass-Weave Skew / Fiber-Weave Effect

  • From: Scott McMorrow <scott@xxxxxxxxxxxxx>
  • To: Jonas Magnusson <Jonas.Magnusson@xxxxxxxxxxxx>
  • Date: Fri, 5 Dec 2014 22:54:07 -0500

Jonas
It is as good as they say it is.  Near zero skew.

Scott


Scott McMorrow
Teraspeed® Consulting - A Division of Samtec
16 Stormy Brook Rd
Falmouth, ME 04105
(401) 284-1827 Business
http://www.teraspeed.com

On Fri, Dec 5, 2014 at 10:14 PM, Jonas Magnusson <
Jonas.Magnusson@xxxxxxxxxxxx> wrote:

> Gurus, what is your thoughts on the Isola Gigasync mtrl?
>
> Cheers,
> --
> Jonas Magnusson
> Senior Hardware Designer
> Teamleader Hardware design
> Synopsys Hardware Platforms Group
> Synopsys, Inc.
> Kalkstensvägen 3
> SE-224 57 LUND
> SWEDEN
>
> Phone   : +46-46-16 29 05
> Fax     : +46-46-16 29 01
> Cell    : +46-70-89 89 774
> E-mail  : jonasm@xxxxxxxxxxxx
> Web     : www.synopsys.com
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Lee
> Sent: den 5 december 2014 17:18
> To: scott@xxxxxxxxxxxxx; Carson Au
> Cc: Ken Cantrell; Loyer, Jeff; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: AW: Glass-Weave Skew / Fiber-Weave Effect
>
> AH!  The gods again!
>
> -----Original Message-----
> From: Scott McMorrow
> Sent: Friday, December 05, 2014 2:50 PM
> To: Carson Au
> Cc: Ken Cantrell ; Loyer, Jeff ; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: AW: Glass-Weave Skew / Fiber-Weave Effect
>
> One must be patient and wait for the gods to reveal such a material.
> Release is imminent.
>
>
>
>
>
>
> Scott McMorrow
> Teraspeed® Consulting - A Division of Samtec
> 16 Stormy Brook Rd
> Falmouth, ME 04105
> (401) 284-1827 Business
> http://www.teraspeed.com
>
> On Fri, Dec 5, 2014 at 5:41 PM, Carson Au <carson.au@xxxxxxxxx> wrote:
>
> > What are these spread-independent materials? I only know of Isola's
> > Gigasync.
> >
> > On Sat, Dec 6, 2014 at 9:28 AM, Ken Cantrell <ken@xxxxxxxxxxxxxxxx>
> wrote:
> >
> >> Jeff,
> >> Give him the money!! :)
> >>
> >> Ken
> >>
> >> -----Original Message-----
> >> From: si-list-bounce@xxxxxxxxxxxxx
> >> [mailto:si-list-bounce@xxxxxxxxxxxxx]
> >> On Behalf Of Scott McMorrow
> >> Sent: Friday, December 05, 2014 3:00 PM
> >> To: Loyer, Jeff
> >> Cc: si-list@xxxxxxxxxxxxx
> >> Subject: [SI-LIST] Re: AW: Glass-Weave Skew / Fiber-Weave Effect
> >>
> >> Jeff
> >> on the shining the light thing, that's called an optical densitometer.
> >> you can make one with a calibrated flatbed scanner.  Then it's a
> >> matter of creating a table of optical density vs Er.  It would make
> >> for a nice academic study.
> >>
> >> As for the dozens of materials I've characterized recently, I can
> >> tell you that I have a method that provides a very accurate relative
> >> figure of merit between weave/resin systems in one trace measurement
> >> per laminate stackup, not accounting for non-orthogonality of board
> >> and weave.  A few more traces and I can adjust for weave/board
> misalignment.
> >>
> >>   As for something that gives statistically accurate skew spread
> >> measurements ... nope.  Care to fund the study?  I know how to do it.
> >> Have
> >> known for 10 years  I know the quickest methodology to get the
> >> statistical results.  It's just a matter of sampling quite a few
> >> boards.
> >>
> >>
> >> Scott McMorrow
> >> Teraspeed® Consulting - A Division of Samtec
> >> 16 Stormy Brook Rd
> >> Falmouth, ME 04105
> >> (401) 284-1827 Business
> >> http://www.teraspeed.com
> >>
> >> On Fri, Dec 5, 2014 at 4:39 PM, Loyer, Jeff <jeff.loyer@xxxxxxxxx>
> wrote:
> >>
> >> > Hi Scott,
> >> > Can you share any of the studies you've performed to characterize
> >> > the dozens of materials?  I'm especially interested in clever
> >> > techniques you might have used to ensure you measured the maximum
> >> > for each material, given the statistical nature of the problem
> >> > (whenever I think of performing such a study, I am put off by "how
> >> > do I ensure my data includes some representative 'worst case'?").
> >> >
> >> > To all,
> >> > I believe there is extreme ambiguity in the terms used for spread
> >> > glass, I would be wary of any particular terminology (is "ultra"
> >> > better than "hyper"?).  And, even if you do standardize the
> >> > definition of "spread", the net effect is going to vary
> >> > significantly for the various glass styles
> >> > (1080 will probably always be more problematic than 2116, for
> >> > instance).  I don't know of any method of easily quantifying the
> >> > electrical properties of any particular spread glass.  There is
> >> > work on-going for a visible light test, but as far as I know those
> >> > results have not yet been correlated to Vp differences.
> >> > BTW, this might be a nice opportunity for a clever person to come
> >> > up with an easy (cheap, HVM-compatible) method of shining a light
> >> > through glass weaves and quantifying the difference between the
> >> > brightest and darkest areas - ideal "spread glass" would have very
> >> > little difference, corresponding to very little difference in Vp
> >> > across the
> >> weave.
> >> > And finally, I don't know of any silicon solutions, ours or
> >> > otherwise, used explicitly to solve the fiberweave issue.  Adaptive
> >> > equalization may make it less of an issue than it was previously,
> however.
> >> >
> >> > Jeff Loyer
> >> >
> >> >
> >> > -----Original Message-----
> >> > From: si-list-bounce@xxxxxxxxxxxxx
> >> > [mailto:si-list-bounce@xxxxxxxxxxxxx]
> >> > On Behalf Of Scott McMorrow
> >> > Sent: Friday, December 05, 2014 5:42 AM
> >> > To: Havermann, Gert
> >> > Cc: billh@xxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> >> > Subject: [SI-LIST] Re: AW: Glass-Weave Skew / Fiber-Weave Effect
> >> >
> >> > Gert,
> >> > Even flat weaves have skew, as easily evidenced by a picture of the
> >> > weave that shows gaps in the overlap of fiber bundles in one
> direction.
> >> >
> >> > I've found that the killer problem is skew on line cards causing
> >> > diff to common mode conversion that bursts as crosstalk within
> >> > connector PTH via fields and connectors themselves, which are not
> >> > designed to control common modes.  This was seen specifically in a
> >> > significant loss of NEXT margin at receivers from Tx or Rx card
> >> > skew causing excessive crosstalk in the connector pin fields for a
> >> > well-known standard. This required two solutions, one was to
> >> > guardband margin to allow for the additional skew caused NEXT.  The
> >> > other was to use some
> >> skew abatement methods.
> >> >
> >> > Doing 1000's of sensitivity runs I've found that this skew
> >> > sensitivity is much worse on cards than it is on backplanes.  That
> >> > is, the card skew allowance has much less tolerance than does the
> >> > backplane or total end-to-end skew.  Where the skew is located is
> >> > much more important than how much skew there is.
> >> >
> >> > To put some numbers to this phenomena, a 10G link had 12 ps of
> >> > skew, which translates to around -0.7 dB of additional insertion
> >> > loss.  That is generally not a serious issue for 99.9% of all
> >> > designs.  However when the effective loss due to crosstalk was
> >> > factored in, due to diff to common mode and common mode to diff
> >> > conversion, total additional eye
> >> loss was -3.9 dB.
> >> > which is a huge impairment.
> >> >
> >> > In the end, the only solution for skew, especially at 28G rates and
> >> > above, is to utilize special techniques to mitigate skew on
> >> > backplanes, and skew-free materials on cards.  I've measured and
> >> > characterized dozens of materials and can say that I can easily
> >> > demonstrate the potential for any woven PCB laminate to have
> >> > significant skew, even those with spread weaves, except for those
> >> > laminates that are specifically engineered for zero-skew with
> >> > matched
> >> glass and resin dielectric constants.
> >> >
> >> > Regards,
> >> >
> >> > Scott
> >> >
> >> > Scott McMorrow
> >> > Teraspeed® Consulting - A Division of Samtec
> >> > 16 Stormy Brook Rd
> >> > Falmouth, ME 04105
> >> > (401) 284-1827 Business
> >> > http://www.teraspeed.com
> >> >
> >> > On Fri, Dec 5, 2014 at 3:29 AM, Havermann, Gert <
> >> > Gert.Havermann@xxxxxxxxxxx>
> >> > wrote:
> >> >
> >> > > Hi Bill,
> >> > > I've seen it quite often, but I never seen it killing System
> >> > > performance as we work with good margin, and the Silicon accepts
> >> > > even more skew that expected.
> >> > > One Design was not usable due to weave effect skew. It was a TRL
> >> > > Cal.Stucture where the shortest line hat skew exceeding the Phase
> >> > > difference. After that I redesigned with different Material and
> >> > > flat weave Glass, and that worked great.
> >> > >
> >> > > BR
> >> > > Gert
> >> > >
> >> > >
> >> > > ----------------------------------------
> >> > > Absender ist HARTING Electronics GmbH, Marienwerderstraße 3,
> >> > > D-32339 Espelkamp; Registergericht: Amtsgericht Bad Oeynhausen;
> >> Register-Nr.:
> >> > > HRB 8808; Vertretungsberechtigte Geschäftsführer: 
> >> > > Dipl.-Kfm.
> >> > > Edgar-Peter Düning, Dipl.-Ing. Torsten Ratzmann,
> >> Dipl.-Wirtschaftsing.
> >> > > Ralf Martin Klein
> >> > >
> >> > > -----Ursprüngliche Nachricht-----
> >> > > Von: si-list-bounce@xxxxxxxxxxxxx
> >> > > [mailto:si-list-bounce@xxxxxxxxxxxxx]
> >> > > Im Auftrag von Bill Hargin (Nan Ya, USA)
> >> > > Gesendet: Freitag, 5. Dezember 2014 06:04
> >> > > An: si-list@xxxxxxxxxxxxx
> >> > > Betreff: [SI-LIST] Glass-Weave Skew / Fiber-Weave Effect
> >> > >
> >> > > Hi Folks …
> >> > >
> >> > > I’m doing a bit of research on glass-weave skew / the
> >> > > fiber-weave
> >> effect.
> >> > > I’ve read the articles/presentations, and understand 
> >> > > the
> >> > > nature of the beast, but I’m interested in getting 
> >> > > data
> >> > > from the design
> >> trenches.
> >> > >
> >> > > Are you (or do you believe you’ve) seen it in your 
> >> > > designs?
> >> > > What
> >> > > happened, and how did you resolve it?  (E.g., angled routing,
> >> > > low-Dk glass, homogeneous resin/glass, etc.)  What were the
> >> > > characteristics of the material and signals?
> >> > >
> >> > > I have no idea what I’m going to hear in response, 
> >> > > but if
> >> > > you respond offline, I’ll hold the info you provide in
> confidence.
> >> > > If
> >> > > you reply publicly – I promise not to share your 
> >> > > secrets
> >> > > beyond the SI-List …
> >> > >
> >> > > Bill Hargin
> >> > > Director of North American Sales / Marketing Nan Ya Copper-Clad
> >> Laminates
> >> > > billh@xxxxxxxxxxxxx   â–ª  425-301-4425  â–ª 
> >> > >  Skype:
> >> > > bill.hargin
> >> > >
> >> > >
> >> > >
> >> > >
> >> > >
> >> > >
> >> > >
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