[SI-LIST] Re: Fiber weave effect modeling: Stack of materials ...
- From: Hermann Ruckerbauer <hermann.ruckerbauer@xxxxxxxxxxxxx>
- To: "Loyer, Jeff" <jeff.loyer@xxxxxxxxx>
- Date: Fri, 05 Aug 2011 19:47:16 +0200
Hello Jeff, Steve,
one more time: thanks for your feedback!
Hermann
EKH - EyeKnowHow
Hermann Ruckerbauer
www.EyeKnowHow.de
Hermann.Ruckerbauer@xxxxxxxxxxxxx
Veilchenstrasse 1
94554 Moos
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schrieb Loyer, Jeff:
> It turns out that we built some test boards with this exact configuration and
> got the answer you predict, though I'm not absolutely sure it was due solely
> to the 1080 alignment - these particular boards had the microstrip fiberglass
> skewed about 1 degree relative to the board edge, so that might have had some
> effect also. But, the cross-sections showed the glass bundles aligning
> randomly (Hermann, see attached; sorry others, you won't be able to see it),
> so I think you'd get the desired effect. I'm not sure you could guarantee
> that you'd never get the worst-case alignment of all the bundles either,
> though it seems unlikely you'd get it often.
>
> Unfortunately, you're also back to specifying your exact stackup, which some
> vendors might accommodate and some might not. And, as Steve pointed out,
> you're forcing larger geometries.
>
> Jeff Loyer
>
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
> Behalf Of Hermann Ruckerbauer
> Sent: Friday, August 05, 2011 1:44 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [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
> Mobile: +49 (0)176 / 787 787 77
> Fax: +49 (0)3212 / 121 9008
>
>
> 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
>> >>
>> >>
>> >>
>> --------------------------------------------------------------------------
>> >> Absender ist HARTING Electronics GmbH & Co. KG; Sitz der Gesellschaft:
>> >> 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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