[SI-LIST] Re: FR4
- From: "Rich Peyton" <p2rich@xxxxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Wed, 11 Jul 2001 07:42:25 -0400
Thanks All,
Before I got any replies I found a Reference that stated FR4= 4.5 +/- 0.5
which is pretty close to all replies.
Thanks,
Rich
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Martyn Gaudion
Sent: Tuesday, July 10, 2001 4:57 PM
To: si-list@xxxxxxxxxxxxx
Cc: Rich Peyton
Subject: [SI-LIST] Re: FR4
Rich,
Its well worth taking a look at the laminate vendors web sites.
It is also worth noting that FR4 is a resin glass
composite based on Glass with Er of around 6 and
resin with Er of around 3.
If you are designing differential traces on fine
spacings you need to take this into account.
Typically most fabricators use 4.3 or 4.2 for single
ended designs, but for close spaced differential traces
they use 3.6 to 3.8
An explanation of this effect is here:
www.polarinstruments.com/support/cits/AP139.html
Kind regards
Martyn Gaudion
At 13:57 10/07/01 -0400, you wrote:
>Hi
>
>what is the dielectric constant for FR4? Or a web site with listing of
>typical materials and there constants?
>
>Thanks,
>Rich
>
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