RE: [SI-LIST] : Impact of halogen-free boards

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From: Kai Keskinen (keskinen@nortelnetworks.com)
Date: Mon Nov 27 2000 - 09:35:35 PST


The place to find the answers to the new board material characteristics is
with the manufacturers of the board materials. You could start with NELCO
(www.parknelco.com) and Rodgers (www.rogers-corp.com). It appears that the
bulk of the raw material is produced in Japan and is made into the board
materials in the US.

Cheers,

Kai Keskinen
Equipment and Network Interconnect
Nortel Subsystems and Performance Networks (NSPaN)
(613)-765-3506 (ESN 395)
keskinen@nortelnetworks.com

> -----Original Message-----
> From: Ole Segtnan [SMTP:ole.segtnan@era.ericsson.se]
> Sent: Monday, November 27, 2000 10:34 AM
> To: si-list@silab.eng.sun.com
> Subject: [SI-LIST] : Impact of halogen-free boards
>
> Hi all,
>
> I would like to bring up the issue of halogen-free materials vs. signal
> integrity.
>
> Most of us will probably need to replace the traditional board materials
> such as FR4 by halogen-free materials in the near future. As a result,
> impedances, losses, etc. will change, but how? I would be grateful for
> any experience, information and comments!
>
> I realize that this may be a huge question but maybe we can break it in
> two:
>
> 1/ Material "constants":
> - What are the values of epsilon, conductivity, etc. of these new
> materials?
> - How do these "constants" vary with frequency?
>
> 2/ Impact on impedances, losses, etc.
> - Which changes are important?
>
> One particular material was measured to differ in the following way
> compared to FR4:
> - epsilon increased by 10%
> - loss tangent increased by 60%
> No other significant differences were seen.
>
> In my opinion, this will give the following effects:
> - Signal velocity reduction (about 3%) is negligible.
> - Impedance change can be compensated by means of track width.
> - Increased dielectrical loss may be a problem.
>
> Any comments?
>
> Best Re
> --
> Ole Segtnan
> Ericsson Radio Systems, Stockholm
> Phone: +46 8 585 32 279
>
>
>
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