From: Ole Segtnan (firstname.lastname@example.org)
Date: Mon Nov 27 2000 - 07:34:05 PST
I would like to bring up the issue of halogen-free materials vs. signal
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
1/ Material "constants":
- What are the values of epsilon, conductivity, etc. of these new
- 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.
-- Ole Segtnan Ericsson Radio Systems, Stockholm Phone: +46 8 585 32 279
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