Your RF guy might be correct.
For RF applications using Epoxy blended materials I usually specify the
laminate.  Two that come to mind are Getek, and Nelco 4000-13.  There are many
others which are blended for high-speed, low-loss operations.  There actually is
a wide range of materials which can qualify as FR-4, with a wide range of
electrical properties at 'higher' frequencies.

Even with the same resin, the dielectric constant for them material on 7628
glass might be 4.6, and on 106 glass might 4.1.  Why?  because the resin %
changes from 40% to 75% and the glass has a dielectric constant of over 6, and
the resin has a constant of around 3.



George Franck
"My Opinions are just that"


Ron Luman wrote:

> 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]
>