[SI-LIST] Re: AW: fiber weave effect
- From: kelvin.harding@xxxxxxxxxxxxxxx
- To: si-list@xxxxxxxxxxxxx
- Date: Fri, 15 Aug 2014 23:12:12 +0100
Hi Lee,
How would you tackle a large FPGA on a small PCB with more than 140 diff
pairs.
If there is not enough room to split the pair to route between BGA
pads/vias and not enough board area for loosely coupled pairs what are
the options?
Regards,
Kelvin
On 2014-08-15 21:58, Lee wrote:
> Ken,
>
> What do you mean by elaborate?
>
> -----Original Message-----
> From: Ken Cantrell
> Sent: Friday, August 15, 2014 12:44 PM
> To: leeritchey@xxxxxxxxxxxxx ; shlepnev@xxxxxxxxxxxxx ;
> jeff.loyer@xxxxxxxxx
> ; Gert.Havermann@xxxxxxxxxxx ; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: AW: fiber weave effect
>
> Lee,
> Would you like to elaborate on your "for the record" statement?
>
> Thanks,
>
> Ken
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx] On
> Behalf Of Lee
> Sent: Friday, August 15, 2014 11:38 AM
> To: shlepnev@xxxxxxxxxxxxx; jeff.loyer@xxxxxxxxx;
> Gert.Havermann@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: AW: fiber weave effect
>
> Ah! Since then we have built several more test PCBs using other glass
> styles with great results. The DesignCon 2013 paper was the stimulus
> for
> building more test PCBs including some using GigaSync with results
> similar
> to yours. We are about to build several more.
>
> What we learned with the DesignCon paper is that there are two
> different
> versions of 3313 weave, one that is mechanically spread in both
> directions
> and one that is mechanically spread in only one direction- the weave
> used in
> the DesignCon paper. You can see that skew in on axis is very good and
> in
> the other it is poor.
>
> Out of this has grown a movement to define what mechanically spread
> means.
> We are a long way from getting this one settled.
>
> For the record, I never use tightly coupled traces. There are too many
> down
> sides and very few up sides.
>
> -----Original Message-----
> From: Yuriy Shlepnev
> Sent: Friday, August 15, 2014 10:06 AM
> To: 'Lee ' ; jeff.loyer@xxxxxxxxx ; Gert.Havermann@xxxxxxxxxxx ;
> si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: AW: fiber weave effect
>
> Hi Lee,
>
> For the test boards (there were a few) we used Isola's I-SPEED with
> 3313
> glass on one side. As follows from your DesignCon 2013 paper, you
> observed
> 59 ps maximal skew for 14' horizontally oriented lines (table on page
> 10)
> for that specific case - did I miss something?
> Isola's GigaSync on 2116 glass was used on the other side of the board.
> There were no measurable differences in the skew for the tightly
> coupled
> traces between two materials. The skew was actually too small to make
> any
> conclusions in both cases. However, GigaSync produced smaller far-end
> mode
> transformation, that looks like much better metric for the material
> inhomogeneity, comparing to the direct skew comparison (especially for
> the
> tightly coupled traces).
>
> 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
> Simbeor - Accurate, Fast, Easy and Affordable Electromagnetic Signal
> Integrity Software
> 2010 and 2011 DesignVision Award Winner
>
>
> -----Original Message-----
> From: Lee [mailto:leeritchey@xxxxxxxxxxxxx]
> Sent: Friday, August 15, 2014 9:47 AM
> To: shlepnev@xxxxxxxxxxxxx; jeff.loyer@xxxxxxxxx;
> Gert.Havermann@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: Re: [SI-LIST] Re: AW: fiber weave effect
>
> We have built many test PCBs with a variety of glass weaves of
> mechanically
> spread glass, done for laser drilling not SI, to see what control can
> be had
> over skew using such materials. The results have been very good. Skew
> of
> less than 2-3 pSec over 16". We have also evaluated two materials from
> Isola designed to minimize skew and found similar excellent results.
>
> These are GigaSync and a new material tentatively called ISE-41. They
> provide very low skew, independent of the glass weave style.
>
> -----Original Message-----
> From: Yuriy Shlepnev
> Sent: Friday, August 15, 2014 9:17 AM
> To: jeff.loyer@xxxxxxxxx ; Gert.Havermann@xxxxxxxxxxx ;
> si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: AW: fiber weave effect
>
> Hi Jeff,
>
> Thank you for the comments. The numerical experiment actually predicts
> your
> "intuitive" conclusion on the relationship between trace pair
> dimensions and
> observed skew (even for not spread glass type). I just did not find
> published confirmation of that observation. Considering the
> experimental
> data, we will follow your advice and try to make it less "anecdotal"
> :-)
>
> I totally agree with you on the need for the statistical investigation
> of
> the effect. To make it possible, the first step is to develop a fast
> macro-model for transmission line with inhomogeneous and possibly
> pseudo-random distribution of the dielectric properties along and
> across.
> Development of such model was the focus of the theoretical part of the
> paper
> - how to make dielectric properties change along and across the line
> similar
> to the behavior of composite and without violation of casualty. The
> first
> application was to evaluate the worst case scenario. The next
> application
> would be statistical analysis. Though, as you mentioned, the actual
> distribution of the dielectric properties is the unknown so far.
>
> Are those data below for the single-ended traces?
> Did you investigate the tightly-coupled traces?
>
> 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
> Simbeor - Accurate, Fast, Easy and Affordable Electromagnetic Signal
> Integrity Software
> 2010 and 2011 DesignVision Award Winner
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx] On
> Behalf Of Loyer, Jeff
> Sent: Friday, August 15, 2014 8:23 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
> 5
> -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
> 5
> -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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> Espelkamp; Registergericht: Amtsgericht Bad Oeynhausen; Register-Nr.:
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>
> -----UrsprЭngliche 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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