[SI-LIST] Re: Er range of FR4
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "Zanella, Fabrizio" <fzanella@xxxxxxxxxxxxx>, Aubrey_Sparkman@xxxxxxxx, Charles.Grasso@xxxxxxxxxxxx
- Date: Mon, 8 Aug 2005 09:06:49 -0700
As someone pointed out, the Nelco web site has good data on all of the
materials they produce ranging from the stuff we call FR-4 to 4000-13SI.
The er varies with both glass to resin ratio and frequency. I have
attached a spreadsheet for what is called HiTg Fr-4. Notice that for 4
mils of thickness there are three possible choices with a significant
spread in er. For this reason, the stackup needs to call out which
formulation (glass to resin ratio) is to be used.
When I design stackups, I work with the engineering department of my chosen
fabricators and we work out the optimum combination of thicknesses and
glass to resin ratios. Once we agree, these are specified on the
fabrication drawing and are no longer negotiable.
A subtle problem with PCBs that have GB+ signalling is the potential for
jitter resulting from the use of large glass weave fibers that cause the er
to vary across a given layer. Several people have studied this and some
papers have been written on it. I believe engineers at Intel have reported
on it and someone indicated that they would present a paper on it at
Designcon.
Lee W. Ritchey
Speeding Edge
P. O. Box 2194
Glen Ellen, CA 95442
Phone- 707-568-3983
FAX- 707-568-3504
I just used the energy it took to be angry to write some blues.
Count Basie
> [Original Message]
> From: Zanella, Fabrizio <fzanella@xxxxxxxxxxxxx>
> To: <Aubrey_Sparkman@xxxxxxxx>; <Charles.Grasso@xxxxxxxxxxxx>
> Cc: <si-list@xxxxxxxxxxxxx>
> Date: 8/2/2005 12:50:41 PM
> Subject: [SI-LIST] Re: Er range of FR4
>
> Aubrey, Charles, for correct calculation of impedance with 2D field
> solvers, I use a dielectric constant of 3.8-4.0 for FR4, depending on
> the laminate thickness. I've found this range of values to match
> impedance measurements and calculations by board vendors.
>
> Fabrizio Zanella
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Aubrey_Sparkman@xxxxxxxx
> Sent: Tuesday, August 02, 2005 2:48 PM
> To: scott@xxxxxxxxxxxxx; Charles.Grasso@xxxxxxxxxxxx
> Cc: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Er range of FR4
>
> When I just care about min and max flight times I have been using 3.5 to
> 4.5. But I know there are some materials with vendor data at 4.6 or
> more.
>
> I would also like to know what others are using.=3D20
>
>
> Aubrey Sparkman=3D20
> Enterprise Engineering Signal Integrity Team
> Dell, Inc.=3D20
> Aubrey_Sparkman@xxxxxxxx=3D20
> (512) 723-3592
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Scott McMorrow
> Sent: Tuesday, August 02, 2005 1:36 PM
> To: Charles.Grasso@xxxxxxxxxxxx
> Cc: 'si-list@xxxxxxxxxxxxx'
> Subject: [SI-LIST] Re: Er range of FR4
>
> Charles,
>
> It depends upon the stackup used. I would suggest that you go to the
> Park Nelco website and signup for their dielectric calculator. It is
> very useful for calculating the average Er for any particular laminate
> lay up. Beyond that, localized Er variations are bounded by the Er of
> epoxy and glass (3.2 and 5.6 by weight, respectively.)
>
> scott
>
> Scott McMorrow
> Teraspeed Consulting Group LLC
> 121 North River Drive
> Narragansett, RI 02882
> (401) 284-1827 Business
> (401) 284-1840 Fax
>
> http://www.teraspeed.com
>
> Teraspeed(r) is the registered service mark of Teraspeed Consulting
> Group LLC
>
>
>
> Grasso, Charles wrote:
>
> >Hi - What is the industry accepted range of FR4?
> >I have been using 3.5 - 5. Does that seem correct?
> >
> >=3D20
> >
> >Best Regards
> >Charles Grasso
> >Senior Compliance Engineer
> >Echostar Communications Corp.
> >Tel: 303-706-5467
> >Fax: 303-799-6222
> >Cell: 303-204-2974
> >Pager/Short Message: 3032042974@xxxxxxxx <mailto:3032042974@xxxxxxxx>
> >Email: charles.grasso@xxxxxxxxxxxx;
> >Email Alternate: chasgrasso@xxxxxxxx
> >
> >=3D20
> >
> >
> >
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-- Binary/unsupported file stripped by Ecartis --
-- Type: application/vnd.ms-excel
-- File: NelcoFR4Data.xls
-- Desc: NelcoFR4Data.xls
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