[SI-LIST] Re: AW: fiber weave effect
- From: "Loyer, Jeff" <jeff.loyer@xxxxxxxxx>
- To: Istvan Nagy <buenos@xxxxxxxxxxxxx>, "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Fri, 15 Aug 2014 16:10:55 +0000
Wow - what a collection of data!!! Thanks for sharing.
I haven't studied the spread glasses extensively, but may do so soon - I
appreciate your insights.
Jeff Loyer
-----Original Message-----
From: buenos@xxxxxxxx [mailto:buenos@xxxxxxxx] On Behalf Of Istvan Nagy
Sent: Friday, August 15, 2014 9:05 AM
To: Loyer, Jeff; Gert.Havermann@xxxxxxxxxxx; shlepnev@xxxxxxxxxxxxx;
si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: AW: fiber weave effect
Hi,
I agree it is statistical. How luckily or unluckily the traces are aligned with
the fiber weave.
With spread glass the chances or probability of unfortunate alignment are
reduced, but not eliminated.
The other thing is for product development we have to ensure a good production
yield, so we have to consider worst-case alignment, instead of a statistical
"mean". For hardware design everything is considered worst-case.
Some high-cost boards with high-cost components (some of our boards have
production cost of $3k-$6k with all soldered components) must have 99-100%
yield, so that have to be considered in the statistical assessment. Some lower
cost ($10-20) boards may afford 90% yield, if they can save big on material
cost.
Have you checked photos of the glass fabrics to see how much percentage of the
area is covered with 2-thread, 1-thread, and no-thread? Also some materials can
be classified as 1D spread, some better ones as 2D spread.
Please check my glass fabric photo collection in this document on the second
tab:
http://www.buenos.extra.hu/download/PCB_MATERIAL_LIBRARY.xls
Istvan Nagy
Principal HW Engineer
Fortinet, Sunnyvale
-----Original Message-----
From: Loyer, Jeff
Sent: Friday, August 15, 2014 8:22 AM
To: Gert.Havermann@xxxxxxxxxxx ; shlepnev@xxxxxxxxxxxxx ; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: AW: fiber weave effect
I agree with Gert. I'm also sure there is quite a bit of information about the
effect of spread glass on FWE (Lee Ritchey, Isola, NovaSpeed,
Compunetics?). And it seems intuitive that trace dimensions, relative to
the weave, would influence the skew predictably. To my thinking, having traces
very close together, such that their environment is more similar, should reduce
the skew (since the glass is typically a little larger than the traces).
I would also stress the need for any FWE study to use many boards with many
instances of test structures on each board to accurately evaluate the effect.
They are very subject to random effects which cannot be controlled:
* Exact trace alignment to glass
* Glass alignment to panel edge
o May be different for warp vs. fill
* Wandering of glass
o Will be different for warp vs. fill
Without many samples, you may draw erroneous conclusions from anecdotal
evidence.
For instance, below is a plot of skew between the "p" and "n" of several
samples on our 10 original test boards (the 10" coupons). Note the significant
difference in skew, depending on the particular sample. If you happened to
measure "Bd10", you would conclude a maximum of 30ps of skew; "Bd9" would only
have 5ps of skew (these boards were part of the same build, manufactured
identically at the same time).
Here's the raw data, in case the figure doesn't come out (2 different formats,
raw text and original format):
0 Degree Rotation with soldermask
Bd1 Bd2 Bd3 Bd4 Bd5 Bd7 Bd8 Bd9 Bd10
Layer Orientation Length Sample Direction Polarity
Sample ID "skew (p2-p1)
(+ = m1 on left)"
1 V 10 01 1 1 LYR01OVL10S01D1 1 1
9 6 -1 -3 -3 5 -4
1 V 10 02 1 1 LYR01OVL10S02D1 5
0 -7 -2 3 3 5 -3 12
1 V 10 03 1 1 LYR01OVL10S03D1 0 2
8 5 -2 0 -4 4 -15
1 V 10 04 1 1 LYR01OVL10S04D1 6
1 -9 -3 5 0 5 -3 20
1 V 10 05 1 1 LYR01OVL10S05D1 -2 0
10 9 -3 0 -3 2 -20
1 V 10 06 1 1 LYR01OVL10S06D1 9
0 -9 -4 5 0 4 2 23
1 V 10 07 1 1 LYR01OVL10S07D1 -1 3
9 7 -2 0 -2 0 -22
1 V 10 08 1 1 LYR01OVL10S08D1 8
1 -5 -4 5 -1 3 3 29
1 V 10 09 1 1 LYR01OVL10S09D1 -4 -2
5 7 -4 3 -3 -1 -26
1 V 10 10 1 1 LYR01OVL10S10D1 10
-3 -2 4 -3 2 6 26
0 Degree Rotation with soldermask Bd1 Bd2 Bd3 Bd4 Bd5
Bd7 Bd8 Bd9 Bd10
Layer Orientation Length Sample Direction Polarity
Sample ID skew (p2-p1)
(+ = m1 on left)
1 V 10 01 1 1 LYR01OVL10S01D1 1 1
9 6 -1 -3 -3 5 -4
1 V 10 02 1 1 LYR01OVL10S02D1 5
0 -7 -2 3 3 5 -3 12
1 V 10 03 1 1 LYR01OVL10S03D1 0 2
8 5 -2 0 -4 4 -15
1 V 10 04 1 1 LYR01OVL10S04D1 6
1 -9 -3 5 0 5 -3 20
1 V 10 05 1 1 LYR01OVL10S05D1 -2 0
10 9 -3 0 -3 2 -20
1 V 10 06 1 1 LYR01OVL10S06D1 9
0 -9 -4 5 0 4 2 23
1 V 10 07 1 1 LYR01OVL10S07D1 -1 3
9 7 -2 0 -2 0 -22
1 V 10 08 1 1 LYR01OVL10S08D1 8
1 -5 -4 5 -1 3 3 29
1 V 10 09 1 1 LYR01OVL10S09D1 -4 -2
5 7 -4 3 -3 -1 -26
1 V 10 10 1 1 LYR01OVL10S10D1 10
-3 -2 4 -3 2 6 26
In my experience, FWE is a statistical beast which doesn't easily lend itself
to precise analysis. We're missing some critical information, such as the
statistical distribution of weave wandering. But, I welcome all efforts to
quantify it better.
Thanks for sharing,
Jeff Loyer
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Havermann, Gert
Sent: Friday, August 15, 2014 7:35 AM
To: shlepnev@xxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] AW: fiber weave effect
Hello Yuriy,
I'm not surprised that tight coupling is less attracted to weave effect on
3313 glass.
Mechanically spoken, tighter coupling decreases the dielectric differences in
between traces of a differential pair. Look at Figure 5 of your paper and
imagine what the difference of effective dielectric surrounding the traces
would be when the spacing is close to one tracewidth. The difference would be
very small, especially when flat weave or even flattened weave is used.
BR
Gert
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-----Ursprüngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx<mailto:si-list-bounce@xxxxxxxxxxxxx>
[mailto:si-list-bounce@xxxxxxxxxxxxx] Im Auftrag von Yuriy Shlepnev
Gesendet: Freitag, 15. August 2014 16:08
An: si-list@xxxxxxxxxxxxx<mailto:si-list@xxxxxxxxxxxxx>
Betreff: [SI-LIST] fiber weave effect
Hello Everyone,
Some results of our on-going investigation of fiber-weave effect (FWE) were
recently presented at IEEE EMC 2014 symposium (at SIPI section) and the paper
and presentation are now available at http://www.simberian.com/AppNotes.php -
see #2014_04.
One of the interesting outcomes was practically negligible FEW impact on the
tightly coupled traces on spread fiber fabric (voltage coupling coefficient
about 0.2). We have observed it both on strip and micro-strip (one sheet of
dielectric fabric) configurations.
We did not find any published confirmation of this result. Any comments or
thoughts?
Best regards,
Yuriy
Yuriy Shlepnev, Ph.D.
President, Simberian Inc.
3030 S Torrey Pines Dr. Las Vegas, NV 89146, USA Office +1-702-876-2882; Fax
+1-702-482-7903 Cell +1-206-409-2368; Virtual +1-408-627-7706
Skype: shlepnev
www.simberian.com<http://www.simberian.com>
Simbeor - Accurate, Fast, Easy and Affordable Electromagnetic Signal Integrity
Software
2010 and 2011 DesignVision Award Winner
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