[SI-LIST] Re: Fiber weave effect modeling: Stack of materials ...
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "Al Neves" <al@xxxxxxxxxxxxxxxxx>, "'JASON MILLER'" <jason.miller@xxxxxxxxxx>
- Date: Wed, 10 Aug 2011 10:37:29 -0700
If you want loss, use Isola's FR408HR. It has all the correct weaves and is
bullet proof.
Lee
--------------------------------------------------
From: "Al Neves" <al@xxxxxxxxxxxxxxxxx>
Sent: Wednesday, August 10, 2011 10:02 AM
To: "'JASON MILLER'" <jason.miller@xxxxxxxxxx>; "'Lee Ritchey'"
<leeritchey@xxxxxxxxxxxxx>
Cc: "'Hermann Ruckerbauer'" <hermann.ruckerbauer@xxxxxxxxxxxxx>;
<si-list@xxxxxxxxxxxxx>
Subject: [SI-LIST] Re: Fiber weave effect modeling: Stack of materials ...
> Thanks for the informative thread!
>
> There is always discussion regarding non-homogeneous weave impacting skew,
> period loading (increased loss), mitigating the impact with offset
> designs,
> etc.,
>
> We are designing our 28Gbpsec Channel Modeling Beta Platform and actually
> WANT LOSS (the purpose of the platform is to introduce loss, ISI, for RX
> tolerance, 3D EM analysis, optimization of channels using DFE, FFE, CTLF,
> etc.,) but are concerned that the weave impact, even with offsetting the
> orientation of the t-lines against the fibre weave, will impact launch
> integrity and create a virtual connector repeatability problem (we intend
> on
> using Molex top launch 2.4mm connectors).
>
> Connector repeatability is important for consistent S-parameter
> calibration
> (TRL, unknown THRU or SOLR, AFR, etc.,) and T-matrix de-embedding
> approaches
> used for the platform.
>
> Anyone have insight into how weave impacts launch consistency,
> specifically
> for 2116?
>
>
> Products for the Signal Integrity Practitioner
>
>
> Wild River Technology LLC
>
> Alfred P. Neves
> Founder - Engineer - Business Development
> (503) 718 7172 Office
> (503) 679 2429 Mobile
> 735 South East 16th Ave.
> Hillsboro, OR 97123
> www.wildrivertech.com
>
>
>
>
>
>
>
>
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On
> Behalf Of JASON MILLER
> Sent: Wednesday, August 10, 2011 7:37 AM
> To: Lee Ritchey
> Cc: Hermann Ruckerbauer; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Fiber weave effect modeling: Stack of materials ...
>
> I just want to mention that there are other considerations when it comes
> to weave effects, such as periodic loading of the trace by the glass
> weave, which don't get simply resolved by the first approach of routing
> at an angle relative to the weave. There are a couple of papers in
> recent years that I am aware of which detailed this:
> http://www.electrical-integrity.com/Paper_download_files/DC10_7-WA1_Miller-B
> lando-Novak.pdf
> http://www.founderpcb.com/upfile/File/2011/SI_Glassweave_Isola_DesignCon2011
> %2820110727%29.pdf
>
> On the other hand, tightening the weave or spreading out the glass
> fabric *will* improve the uniformity of the dielectric and mitigate the
> effect of the glass-weave periodic loading.
>
> Jason Miller
> Oracle
>
>
> Lee Ritchey wrote:
>> I've been on vacation, so come late to this discussion. There are three
>> glass weaves that are irregular enough to cause skew problems with
>> differential pairs as has been shown in papers presented at DesignCon.
>> These are 106 ,1080 and 7628. We've tried various ways of nesting
> multiple
>> plies of these to avoid this problem. Doesn't seem to work all that
>> well.
>>
>> There are some very simple fixes. One is to route the PCB traces at an
> angle
>> to the weave or cock the PCB on the fabrication panel. Both work, but
>> are
>
>> either a hassle or expensive.
>>
>> A much simpler approach is to use a glass weave with uniformly
>> distributed
>
>> glass. These are readily available. 1067 replaces 106. 1086 replaces
>> 1080. 3313 in two plies replaces 7628.
>>
>> We've done many tests and demonstrated that the skew problem goes away
> with
>> the use of these weaves. I've got a paper that shows the difference
> between
>> 1080 and 3313. It is dramatic!
>>
>> Lee
>>
>>
>> --------------------------------------------------
>> From: "Hermann Ruckerbauer" <hermann.ruckerbauer@xxxxxxxxxxxxx>
>> 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
>>>> >> 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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>
> --
> Oracle <http://www.oracle.com>
> JASON R. MILLER | PRINCIPAL HARDWARE ENGINEER
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> 35 NETWORK DRIVE | BURLINGTON, MA 01803
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