[SI-LIST] AW: Fiber weave effect modeling: Stack of materials ...
- From: "Havermann, Gert" <Gert.Havermann@xxxxxxxxxxx>
- To: "Hermann Ruckerbauer" <hermann.ruckerbauer@xxxxxxxxxxxxx>, si-list@xxxxxxxxxxxxx
- Date: Mon, 8 Aug 2011 13:00:57 +0200
Hi Herman,
I once read an article or paper (or something else) about stacking 106 with the
goal to mesh the weave to get a homogenious glass fill. Unfortunately I don't
know where I read it, and I can't find it on my computer or in web, thus it
might have been in the documentation of our customers.
But, I know that the final result was that the glass did mesh very nicely, but
not on the complete PCB. There were always areas of weave effect potential.
They also calculated the possibility that a trace will see weave effect (taking
into account assumptions on PCB space, design grid, ammount of traces per
layer...), but the number was still not low enough to have a 99% weave free
design.
Hope this helps.
BR
Gert
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-----Ursprüngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im
Auftrag von Hermann Ruckerbauer
Gesendet: Freitag, 5. August 2011 10:44
An: si-list@xxxxxxxxxxxxx
Betreff: [SI-LIST] Fiber weave effect modeling: Stack of materials ...
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
> >> 8808; Geschäftsführer: Edgar-Peter Duening, Torsten Ratzmann, Dr.
> >> 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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