[SI-LIST] AW: AW: Fiber weave effect modeling

  • From: "Havermann, Gert" <Gert.Havermann@xxxxxxxxxxx>
  • To: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>, si-list@xxxxxxxxxxxxx
  • Date: Fri, 14 Jan 2011 09:34:44 +0100

Hi Lee,

this is really interesting. I knew that the 2113 is quite uniform as is uses 
thin glass filaments, but I've never heard of the other glass styles. I just 
checked with ISOLA and NELCO low loss materials, and couldn find the other 
types either. Could it be they are only used for lossy FR4 Type of materials, 
or just by certain vendors? 

BR
Gert


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Von: Lee Ritchey [mailto:leeritchey@xxxxxxxxxxxxx] 
Gesendet: Donnerstag, 13. Januar 2011 19:22
An: Havermann, Gert; si-list@xxxxxxxxxxxxx
Betreff: Re: [SI-LIST] 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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