I have not done RF work for many years, but I wouldn't trust FR4 as an RF
material even if you specified it - how could you be certain you got what you
specified?  There are other board materials that are specifically designed for
controlled impedance situations.  You want a material that does not soak up
moisture as that will also affect the REAL dielectric constant, no matter what
you start out with.

Bob Landman
H&L Instruments

----- Original Message -----
From: Ron Luman <[log in to unmask]>
To: <[log in to unmask]>
Sent: September 27, 1999 11:00 AM
Subject: [DC] RF boards


> I am having a problem with the RF engineer saying the board material
> (vendor) is the problem with his circuit not working. In every formula I
> have looked at the dielectric constant of FR4 is the same.
> My boards are .062 thick FR4 Tg 130. no soldermask no silkscreen.
> Can someone out there explain to me what the differences can be between two
> vendors when they are both using the same process notes I supply to make the
> boards??
> And how this might effect the RF circuit?
> Thank You
>
> Ronny Luman C.I.D.
> SERCEL INC.
> (918) 621-5725
> [log in to unmask]
>