Hi Lee,
So true...
Recently we did a 22-layer stackup. We used 3313 glass and had a month long
interaction with the vendor regarding layer spacings, trace widths, and
trace spacings etc. to make it robust in terms of SI and PI. One day, after
reading one of your DesignCon papers, I just casually asked him if 3313
will be mechanically spread in both directions. His answer after verifying
with his Weaver was a No!
Darn! We had to redesign the whole stack up using glass weave spread in
both directions! It was time consuming, but at least we won't get a shock
at the end when the board will be completed!
Thanks for writing that paper!
Warm regards,
Binayak
On Friday, March 17, 2017, Lee Ritchey <leeritchey@xxxxxxxxxxxxx> wrote:
By the way, this is true of some 3313 weavers, spread in only one
direction.
We got that nasty surprise when we did our test PCBs in 2013. We had been
using laminates with 3313 glass from Matsushita with great skew results and
thought that all 3313 was done that way only to discover it depends on the
weaver.
We have a task force at IPC trying to define what spread glass is so we can
get some consistency in this area.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx <javascript:;> [mailto:
si-list-bounce@xxxxxxxxxxxxx <javascript:;>] On
Behalf Of Boris Bakshan
Sent: Friday, March 17, 2017 10:07 AM
To: Lee Ritchey <leeritchey@xxxxxxxxxxxxx <javascript:;>>
Cc: si-list@xxxxxxxxxxxxx <javascript:;>; dmarc-noreply@xxxxxxxxxxxxx
<javascript:;>
Subject: [SI-LIST] Re: Glass Weave Skew
Hi Lee,
The 1078 and 1035 PLYs of Meg6(G) are MS in just one direction, the Fill
direction. I think I showed you the cross section I did in both Fill and
Warp directions.
On Mar 17, 2017 6:17 PM, "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx
<javascript:;>> wrote:
We have done dozens of designs with spread glass with very good skew<javascript:;>
results. Unfortunately, the most commonly used resin system in low
loss designs is MEG6 which does not offer it.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx <javascript:;>
[mailto:si-list-bounce@xxxxxxxxxxxxx ;<javascript:;>]
On
Behalf Of Loyer, Jeff (Redacted sender "jwloyer" for DMARC)
Sent: Friday, March 17, 2017 7:04 AM
To: bbakshan@xxxxxxxxx <javascript:;>; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Glass Weave SkewSubject field
No. We found the same issue when we investigated the Fiberweave
effect ("Fiber Weave Effect: Practical Impact Analysis and Mitigation
Strategies", 2007). We had several identical boards made and the
measured skew varied significantly. Investigation showed the glass
bundles wandering significantly.
But, many are using "spread glass" and similar techniques to mitigate
the effect.
Jeff Loyer
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx <javascript:;>
[mailto:si-list-bounce@xxxxxxxxxxxxx ;<javascript:;>]
On
Behalf Of Boris Bakshan
Sent: Friday, March 17, 2017 4:23 AM
To: si-list@xxxxxxxxxxxxx <javascript:;>
Subject: [SI-LIST] Glass Weave Skew
Hi experts,
Following Eric's paper on designcon and the conclusions regarding the
inherent misalignment of the glass bundles with respect to the edge of
the board, could it be that some of the laminate manufacturers took
initiative to help mitigating the skew problem caused by the way
fabrics are built for so many years?
(
https://www.signalintegrityjournal.com/ext/resources/article-images-
2017/410
3/4103_SIJ_GlassWeave.pdf
)
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