[SI-LIST] Fiber weave effect modeling: Stack of materials ...
- From: Hermann Ruckerbauer <hermann.ruckerbauer@xxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Fri, 05 Aug 2011 10:44:11 +0200
Hello *,
the original thread is already old, but I would have one more question
on this one:
Will stacks of multiple materials statistically help to reduce the effect ?
"Standard" 1080 looks not too good, but if 2x or 3x 1080 is stacked this
could statistically reduce the effect.
I would not expect that material production and manufacturing is so
accurate that a stack of 3 material will result that always the same
structures are overlayed.
I would more expect, that there might be a statistical distribution for
High volume manufacturing where a part of the final boards will have
this worst case, and on other there will be a statistical distribution
of different combinations how the materials are overlayed in the stack.
Does anybody have more than a feeling on this assumption ?
Thanks and regards
Hermann
EKH - EyeKnowHow
Hermann Ruckerbauer
www.EyeKnowHow.de
Hermann.Ruckerbauer@xxxxxxxxxxxxx
Veilchenstrasse 1
94554 Moos
Tel.: +49 (0)9938 / 902 083
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schrieb Lee Ritchey:
> The 1086 weave used in laser drilled PCBs is the replacement for 1080 and the
> 1067 weave is the replacement for 106 weave. They both look like the Nova
> product and are not subject to patents or single sourcing. 3313 is similar
> and yields a 4 mil core using a single ply of glass.
>
> From: bala
> Sent: Tuesday, January 18, 2011 12:42 AM
> To: Lenkisch, Andreas
> Cc: Lee Ritchey ; Loyer, Jeff ; si-list@xxxxxxxxxxxxx
> Subject: Re: [SI-LIST] AW: Re: AW: Fiber weave effect modeling
>
>
> http://bethesignal.net/blog/?pB
>
>
> On Tue, Jan 18, 2011 at 2:00 PM, Lenkisch, Andreas
> <Andreas.Lenkisch@xxxxxxxxxxx> wrote:
>
> that's really strange, I got the feedback from the PCB shop (Europe) that
> this material is "quite expensive" (about two times more than traditional
> glass weave). The answer is already half a year old. I will ask again.
>
> Andreas
>
>
>
> -----Ursprüngliche Nachricht-----
> Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im
> Auftrag von Lee Ritchey
> Gesendet: Montag, 17. Januar 2011 19:42
> An: Loyer, Jeff; si-list@xxxxxxxxxxxxx
> Betreff: [SI-LIST] Re: AW: Fiber weave effect modeling
>
>
> One thing I forgot to mention in my last response was that the reason we
> switched to 3313 weave was cost reduction, not signal integrity. Prior to
> this material becoming available we achieved 4 mil cores using two plies of
> glass cloth. Our fabricator suggested we switch to 3313 and achieve a lower
> price. I'm not sure why some fabricators would suggest the PCB would cost
> more.
>
> In the bargain, we got the flat weave and much better impedance profiles as
> well as far lower differential skew.
>
> My guess is you won't get the new weaves unless you insist on them.
> Fabricators don't like to expand their inventories unless they are forced
> to. Guess that is like all manufacturers!
>
> --------------------------------------------------
> From: "Loyer, Jeff" <jeff.loyer@xxxxxxxxx>
> Sent: Thursday, January 13, 2011 1:31 PM
> To: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
> Subject: [SI-LIST] Re: AW: Fiber weave effect modeling
>
> > I don't think the elimination of standard weaves is straightforward. I
> > wholeheartedly agree that "flat" weaves exist and are a very attractive
> > solution but, at the time we wrote our paper, they cost about 2x that of
> > standard material. I don't know if the difference is still that high, but
> > I doubt it's insignificant.
> > For many designs, the cost differential is outweighed by the benefits.
> > For others, it is not. 10 degree routing, ugly as it may appear and as
> > time consuming as it is, can be attractive if it saves significant money.
> >
> > On the other hand...
> > There may soon come a point where bus speeds increase such that it is
> > impossible to avoid routing parallel to the board edge for problematic
> > distances. At that point, flat weaves will be a more palatable option.
> > For instance, just breaking out of a large device plus routing into a
> > connector might require 2" of length that can't be angled. For a 40GT/s
> > bus, that's probably unacceptable. Then, the choice gets clearer.
> >
> > For now, many of us are in the grey area where the option of using flat
> > weaves, and getting rid of our funky angled routing, isn't clear-cut.
> >
> > Jeff Loyer
> >
> >
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> > On Behalf Of Lee Ritchey
> > Sent: Thursday, January 13, 2011 10:22 AM
> > To: Havermann, Gert; si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: AW: Fiber weave effect modeling
> >
> > I recommend you use neither of those weaves with high speed serial links
> > due
> > to there negative effect on skew. The best weaves are known as "flat"
> > weaves. The best are 1067 (replaces 106), 1086 (replaces 1080), 2113 and
> > 3313. These are so uniform you don't need to worry about weave effects.
> > These weaves were developed to make laser drilling blind vias more uniform
> > and happen to be great for SI purposes!
> >
> > You also don't need to route your PCBs on a 15 degree angle to the weaves,
> > which is painful to do and wastes materials, so long as you stick with the
> > weaves listed above.
> >
> > Lee Ritchey
> >
> > --------------------------------------------------
> > From: "Havermann, Gert" <Gert.Havermann@xxxxxxxxxxx>
> > Sent: Wednesday, January 12, 2011 6:31 AM
> > To: <si-list@xxxxxxxxxxxxx>
> > Subject: [SI-LIST] AW: Fiber weave effect modeling
> >
> >> this is a great paper, many thanks for sharing it with the si-list.
> >>
> >> please allow me a question. I understand that the 106 and 7628 Prepregs
> >> are used to predict the dk values of "pure epoxy" and "close proximity to
> >> the Glass bundle".
> >> Do you think that the "pure epoxy" value is always the worst case that I
> >> have to expect for my diff pair? If I (for instance) would only use 7628
> >> Style everywhere, will there even be areas "in pure epoxy", or is the
> >> weave dense enough that the worst dk is somewhere between the calculated
> >> min. and max. value?
> >>
> >> BR
> >> Gert
> >>
> >>
> >>
> --------------------------------------------------------------------------
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> >> Espelkamp; Registergericht: Bad Oeynhausen; Register-Nr.: HRA 5596;
> >> persönlich haftende Gesellschafterin: HARTING Electronics Management
> >> GmbH;
> >> Sitz der Komplementär-GmbH: Espelkamp; Registergericht der
> >> Komplementär-GmbH: Bad Oeynhausen; Register-Nr. der Komplementär-GmbH:
> >> HRB
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> >> Alexander Rost
> >> -----Ursprüngliche Nachricht-----
> >>
> >> Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> >> Im
> >> Auftrag von Bert Simonovich
> >> Gesendet: Freitag, 7. Januar 2011 21:55
> >> An: si-list@xxxxxxxxxxxxx
> >> Betreff: [SI-LIST] Fiber weave effect modeling
> >>
> >> Hi all,
> >>
> >> Recently there were discussions on PCB fiber weave effect. I recently did
> >> a study and published a White Paper titled, "Practical Fiber Weave Effect
> >> Modeling".
> >>
> >> Abstract:
> >> Fiber weave effect is becoming more of an issue as bit rates continue to
> >> sore upwards to 5GB/s and beyond. Due to the non-homogenous nature of
> >> printed circuit board laminates, the fiberglass weave pattern causes
> >> signals to propagate at different speeds within differential pair traces;
> >> causing timing skew and mode conversion at the receiver; leading to
> >> reduced bit-error-rate (BER) performance; and increased EMI radiation.
> >> The
> >> relative dielectric constant (Dk) surrounding a trace ultimately
> >> determines its propagation delay. This paper delves into the issue and
> >> presents a novel approach to practically establish worst case min/max
> >> values for Dk and use them to model this effect using ADS circuit
> >> modeling
> >> software. A PCIe CEM
> >> Rev2 case study is used to practically demonstrate the model and to
> >> explore the design space.
> >>
> >> Here is the link: http://lamsimenterprises.com/White_Papers.html
> >>
> >> Thanks to Jeff Loyer, Istvan Novak and Gustavo Blando for there help in
> >> clarifying some results of their prior published work on the subject.
> >>
> >> I hope you find it useful.
> >>
> >> -Bert
> >>
> >> Lambert (Bert) Simonovich
> >> Consultant and Founder
> >> LAMSIM Enterprises Inc.
> >> Web Site: http://lamsimenterprises.com
> >> Blog: http://blog.lamsimenterprises.com/
> >>
> >>
> >>
> >>
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