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"Laminate & prepreg manufacturing - Isola"
On Thu, Jul 1, 2021, 12:34 AM Binayak Shrestha <binayaks@xxxxxxxxx> wrote:
Hi Scott,
If I want to route traces along the fill direction instead of grain
direction, how can I know this information during design/CAD stage - (a)
when fabricator is decided, and (b) when fabricator is not fixed?
Regards,
Binayak
--
Binayak Shrestha
Senior Research Engineer,
C-DOT Centre for Development of Telematics
On Wed, Jun 30, 2021 at 4:23 PM Scott McMorrow <scottmcmorrow@xxxxxxxxx>
wrote:
Rotation generates consistent skew and impedance. Whereas matching pitch
generates only consistent skew, but varying impedance. Rotation is
sufficient as long as all routing is kept away from being parallel to the
weave. Designing traces close to the weave pitch guards against subtle
layout mistakes in trace routing direction.
On Wed, Jun 30, 2021, 3:53 AM heyfitch <dmarc-noreply@xxxxxxxxxxxxx>
wrote:
wrote:
Scott,
Are the items 1 and 2 âeither-orâ?
Do you really need both?
Thanks.
Vadim
On Jun 25, 2021, at 09:36, Scott McMorrow <scottmcmorrow@xxxxxxxxx>
fill
Or close to the weave pitch. On our test boards we:
1) Rotate 22.5 degrees
2) Route at the weave pitch
3) Orient the board so that the predominant trace direction is in the
direction.to
If you can't rotate, then try to have the board oriented on the panel so
that the skew sensitive signals are routed in the fill direction.
If you can't route at the weave pitch, then make the trace pitch closer
the weave pitch than the half-pitch.scottmcmorrow@xxxxxxxxx>
On Fri, Jun 25, 2021 at 12:22 PM Binayak Shrestha <binayaks@xxxxxxxxx>
wrote:
Dear Scott,
Oh! I get it now. Spread glass along with routing differential traces
along the fiber weave pitch has made the skew low.
Thanks for clearing that up for me.
Regards,
Binayak
On Fri, 25 Jun, 2021, 5:18 pm Scott McMorrow, <
weavewrote:
There is nothing inconsistent between Lee and I. He chooses 1067
withdata,specifically because it has an approximate pitch of 14 mil. From our
pitch,the closer the differential trace inter-pair pitch is to the weave
the lower the skew, even in the grain direction.
We built an Examax backplane and line cards without rotation, but
a 14traces oriented predominantly in the fill direction and routed with
4psmil pitch. Skew was well-controlled with a maximum measured skew of
dmarc-noreply@xxxxxxxxxxxxxOn Fri, Jun 25, 2021, 7:21 AM Istvan Novak <
the
wrote:
And we need to remember also that the glass weaves, especially in
Sectiontheirfill direction, are not necessarily straight and they may not keep
angle over a longer stretch. You can see this for instance in
http://www.electrical-integrity.com/Paper_download_files/DC14_14_WE1Paper_SourcesAndCompensationOfSkew.pdfIII.3 in
Sources and Compensation of Skew in Single-Ended and Differential
Interconnects at
contributor toMoreover, as long as skew is not the absolutely dominant
limitfactorsthe degradation of communications, it is just one of the several
that impact the bit error rate. So skew may be at its worst case
thecouple:within its allowed budget, if other contributors (just to name a
crosstalk and reflection due to the statistical nature of stub that
remains after backdrilling) to degradation are not at worst case,
not beforsystem is still OK.
Regards,
Istvan Novak
Samtec
On 6/25/2021 3:49 AM, Havermann Gert (Redacted sender Gert.Havermann
DMARC) wrote:you
Not simple, but important, that's the bad thing about weave effect:
never know when it will hit you. And in mass production you will
strategiesable to test every single trace so it is all about risk management.Knowing
laminate and PCB manufacturing processes helps a lot to find
becauseto
lower the risk.weave
BR
Gert
Von: Binayak Shrestha <mailto:binayaks@xxxxxxxxx>
Gesendet: Freitag, 25. Juni 2021 09:34
An: Havermann, Gert <mailto:Gert.Havermann@xxxxxxxxxxx>
Cc: Si-list <mailto:si-list@xxxxxxxxxxxxx>
Betreff: Re: [SI-LIST] AW: [EXTERNAL] Re: A new old topic - fiber
and low loss materialtake
Dear Gert,
Thank you for explaining in-depth the different scenarios that can
place....not so simple!!!depending
Regards,dmarc-noreply@xxxxxxxxxxxxx> wrote:
Binayak
On Fri, 25 Jun, 2021, 11:13 am Havermann Gert, <mailto:
Dear Binayak,
keep in mind that the weave effect in grain direction is also
on the Laminate manufacturer, and sometimes even on the plant
gives athe
pulling of the weave can be (and in fact is) different.
Another factor is the PCB manufacturer and how he handles a two plyconstruction. Some do very accurate registration stamping which
researchhigher risk of weave effects. So even if you would try to do a
stillon
how much benefit a 2-ply construction would give you, there are
socircumstances,
many unknowns that you may never come to a single conclusion.
Scott has techniques set up to prevent skew under all
skewbut
that doesn't mean that this is the only way to reduce the risk of
manufacturerin
your system. Finding the right combination of material and
Münchencan
have (almost) the same effect (almostÿrphys Law).
BRhttp://www.HARTING.com
Gert
----------------------------------------
HARTING Stiftung & Co. KG | Postfach 11 33, 32325 Espelkamp |
Persönlich haftende Gesellschafterin:
HARTING Führungsstiftung | Amtsgericht München | HRA 108479 |
Dipl.-Kffr.Vorstand: Dipl.-Kfm. Philip F. W. Harting (Vorsitzender),
Harting,Maresa W. M. Harting-Hertz, Dipl.-Kfm. Dr.-Ing. E. h. Dietmar
Dipl.-Ing.Dipl.-Hdl. Margrit Harting, Dr.-Ing. Kurt D. Bettenhausen,
München(FH) Dipl.-Wirtsch.-Ing. (FH) Andreas Conrad, Dr. iur. Michael Pütz9021
Sitz der Gesellschaft: Espelkamp | Amtsgericht Bad Oeynhausen | HRA
| UST-ld Nr. DE812136745
----------------------------------------www.HARTING.com
HARTING Stiftung & Co. KG | Postfach 11 33, 32325 Espelkamp |
Persönlich haftende Gesellschafterin:
HARTING Führungsstiftung | Amtsgericht München | HRA 108479 |
Dipl.-Kffr.Vorstand: Dipl.-Kfm. Philip F. W. Harting (Vorsitzender),
Harting,Maresa W. M. Harting-Hertz, Dipl.-Kfm. Dr.-Ing. E. h. Dietmar
Dipl.-Ing.Dipl.-Hdl. Margrit Harting, Dr.-Ing. Kurt D. Bettenhausen,
mailto:(FH) Dipl.-Wirtsch.-Ing. (FH) Andreas Conrad, Dr. iur. Michael Pütz9021
Sitz der Gesellschaft: Espelkamp | Amtsgericht Bad Oeynhausen | HRA
| UST-ld Nr. DE812136745
-----Ursprüngliche Nachricht-----si-list-bounce@xxxxxxxxxxxxx> Im Auftrag von Binayak Shrestha
Von: mailto:si-list-bounce@xxxxxxxxxxxxx ;<mailto:
Gesendet: Freitag, 25. Juni 2021 06:44
An: Lee Ritchey <mailto:lritchey49@xxxxxxx>
Cc: mailto:scottmcmorrow@xxxxxxxxx; mailto:corley@xxxxxxxxx;
therawilson@xxxxxxxxxxxx; mailto:si-list@xxxxxxxxxxxxx; mailto:low
si-list-bounce@xxxxxxxxxxxxx
Betreff: [EXTERNAL] [SI-LIST] Re: A new old topic - fiber weave and
loss material2-ply
Dear Lee,
The data provided in the Scott's presentation show that even with
construction using spread glass, there can be significant skew in
thatgrain
direction (compared to fill direction) since the spreading effect is
degraded by the pulling of the weave in the grain direction.
Since your data showed less skew in both X and Y directions whileScott's data showed much more skew in grain direction compared to
withgrainin
fill direction, the only conclusion that I think we can arrive at isthat -
using a 2-ply construction does not necessarily reduce the skew in
direction.lritchey49@xxxxxxx>
Regards,
Binayak
---
Binayak Shrestha
Senior Research Engineer,
C-DOT Centre for Development of Telematics
On Thu, Jun 24, 2021 at 11:32 PM Lee Ritchey <mailto:
wrote:
We use two ply 1067 on both sides of a centered stripline layer
lritchey49@xxxxxxxvery good skew results. Both in X and Y directions.
Lee Ritchey
Speeding Edge
P.O. Box 817
Bodega Bay, CA
94923
408-781-0253
mailto:lritchey49@xxxxxxx
Worry is like a rocking chair
It keeps you busy,
but it doesn't get you anywhere.
I just took the energy it takes to get mad and wrote some blues.
Count Basie
-----Original Message-----
From: Binayak Shrestha <mailto:binayaks@xxxxxxxxx>
To: Scott McMorrow <mailto:scottmcmorrow@xxxxxxxxx>
Cc: mailto:corley@xxxxxxxxx; Lee Ritchey ;<mailto:
si-list@xxxxxxxxxxxxx;
mailto:rawilson@xxxxxxxxxxxx; Si-list ;<mailto:
loss;
mailto:si-list-bounce@xxxxxxxxxxxxx
Sent: Thu, Jun 24, 2021 7:48 am
Subject: Re: [SI-LIST] Re: A new old topic - fiber weave and low
sowasmaterial
Hi Scott,
Thanks for sharing the video link. It cleared many of my doubts. I
thinking mechanically spread glass solves the skew problem....not
usingafter
all!
One doubt though - is there any reasonable skew mitigation by
https://blog.samtec.com/post/vehicle-for-insitu-glass-fabric-characterization-edi-con-2017/2-ply
scottmcmorrow@xxxxxxxxx>dielectric construction instead of single-ply construction?
Regards,
Binayak
Warm Regards,
Binayak Shrestha
Senior Research Engineer,
C-DOT Centre for Development of Telematics
On Mon, Jun 21, 2021 at 5:54 PM Scott McMorrow <mailto:
wrote:
Spread fiber only mitigates skew for traces training in the fill
direction. Traces in the grain direction will still have skew.
thebinayaks@xxxxxxxxx>On Sun, Jun 20, 2021, 11:21 PM Binayak Shrestha <mailto:
wrote:
Thanks Scott and Chuck for the information.
As of now, I normally use mechanically spread glass to go around
like asskewnormally
issue. In addition, to make the skew occurrence less likely, I
number ofscottmcmorrow@xxxxxxxxx>tend to go with 2 ply construction.
Thanks,
Binayak
----
Binayak Shrestha
Senior Research Engineer,
C-DOT Centre for Development of Telematics
On Sun, Jun 20, 2021 at 10:15 PM Scott McMorrow <mailto:
wrote:
Isola went through a reorganization that included limiting the
laminates that they would support. GigaSync was cut at that time.
GigaSync worked, but as stated, the loss was higher than we'd
wherewasthat
the Dk. Materials like this try to match the Dk of the polymer to
of
the glass, with some boundary modification also being performed
range.thehigh
polymer and fibers contact. Unfortunately, glass is still fairly
Dk
when compared to the newer polymers that come in the 2.5-2.8
andThe
better bet will be to either use hybrid stackups with mixed woven
varietyskewnon-woven materials, or twin-ax cable flyover technology. Ours is
guaranteed to 3.5 ps skew absolute at 6-sigma confidence. Nominal
iscorley@xxxxxxxxx>
about 1 ps.
On Sun, Jun 20, 2021 at 9:58 AM Chuck Corley <mailto:
wrote:
So far we've been able to deal with fiber weave skew using a
theof
physical layout and laminate construction techniques while using
demandmore common existing PCB materials. It probably reduces the
increasefor
creating a special low skew material while we can manage to keep
continuing to do this fiber weave skew battle by using these
layout/construction techniques with existing materials.
However on the flip side, as the signal speeds continue to
yetthe
fiber weave skew problem becomes more difficult to handle with the
existing PCB laminates. So special materials like GigaSync may
reasonbe
needed in the future. Perhaps the lack of low loss might be a
signalsGigaSync didn't take off. Typically people with high speed
wouldloss.which are fast enough to need low fiber weave skew also need low
I agree with you that some type of low loss version of GigaSync
behave been very nice to have. If such a product could also be
cost-efficient and have good manufacturability, it probably would
is acalledhugely successful.
Chuck
---
Chuck Corley
On 2021-06-19 20:58, Binayak Shrestha wrote:
Hi Lee, Corley, and all:
Few years back, Isola had come up with a dielectric in material
stoppedGigaSync with literally no skew (though not a low loss material).
Is there any specific reason why they stopped producing it and
existed.improving it?
Life would have been so easy if a low loss version GigaSync had
dmarc-noreply@xxxxxxxxxxxxx>Thanks,
Binayak
On Tue, 8 Jun, 2021, 1:29 am Lee Ritchey, <mailto:
wrote:
Ralph,
You would be smart to do this analysis with Isola I-SPEED. It
designdrop
in replacement for 23SI at a much lower cost and much better lossfigures.
In my opinion, 4000-13SI is about obsolete. I sure would not
getCA94923408-781-0253lritchey49@xxxxxxxanything new with it.
Lee RitcheySpeeding Edge
P.O. Box 817Bodega Bay, mailto:
Worry is like a rocking chairIt keeps you busy, but it doesn't
blues.Countyou
anywhere.
I just took the energy it takes to get madand wrote some
defineBasie
-----Original Message-----material
From: Ralph Wilson <mailto:rawilson@xxxxxxxxxxxx>
To: mailto:si-list@xxxxxxxxxxxxx
Sent: Mon, Jun 7, 2021 12:56 pm
Subject: [SI-LIST] Re: A new old topic - fiber weave and low loss
Chuck,
We're in the architecture stage right now on this project. To
usingchannel
routing requirements, I've already done a "what-if" simulation
withNelco-13-SI as a baseline.
With its loss tangent and my system constraints, I have come up
thelosschannelrouting guidelines that allow the channel to meet the PCIe-Gen 4
specifications - just barely. I am right at the limits of allowed
for
the channel. I did a sensitivity analysis to maximize theapplication.
routing length I can allow - which is tight right now in this
Hence, my position is any material "as good as or better" than
tangentNelco should work (where "as good as" generally means a loss
listless than or equal to). Clearly, once we have a final material
selection, have
the stackup defined and the routing is complete we will need to
resimulate to
confirm proper channel operation.
Thanks!
Ralph
On 6/7/2021 12:36 PM, Chuck Corley wrote: Hi Ralph,
There are quite a few good materials now, I would write you a
And Iof
some of the good ones but IâEUR(tm)m not at my desk right now
lowermaterials.donâEUR(tm)t want
to slight any of the great manufacturers who make these good
But I can say there are now less expensive materials that are
youloss
than the one you mentioned.
Before you start shopping for materials though, as a first step
amount ofshould probably calculate the actual loss that you are willing to
tolerate for your communication links. Once you know what
yourloss you can tolerate over the actual worst-case trace lengths
actuallymaterialdesign will have then that will enable you to choose the right
at the best cost. For example, If your longest traces were
andfairly short lengths, then you might be able to use a more lossy
needsignalless expensive PCB material for your design and still meet your
loss targets. Many designs have short trace runs and may not
sincemore
expensive low loss materials.
Chuck
---
Chuck Corley
On 2021-06-07 08:48, Ralph Wilson wrote: It's been a few years
looking atandI've worked with any PCB fab house on
stackups and materials for
high speed SERDES routing, so I've lost track of what is in vogue
at
the knee of the curve
in terms of cost/performance. For the current product I'm
becomeglasswe're "only" dealing with
PCIe-Gen 4 (16Gbps). In "the old days" Nelco-13-SI on a 1080/2116
weavewas a reasonably
priced, low loss, reasonably temperature stable, reasonably flat
moved toproduct applicable
to the 2, 4 and 10G channels of the day. What has the industry
these days?
I fully expect some of yesterdays exotic materials may have
------------------------------------------------------------------cost/performancemainstream and affordable.
What materials and glass weaves are at the knee of the
curve today that
provide a good environment for 16-25Gbps channels?
Thanks!
Ralph Wilson
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