Unfortunately, there are some companies in the high volume RF market that also
need multi-layer RF boards and get their manufacturing overseas. Multi-layer rules
out FR1, and FR2. And, these factories work much different than in the US. It's
very expensive to get other than the standard  materials FR1, FR2, and FR4. Here,
generally speaking, you specify, FR1 or equiv., you'll get a single sided board
that's made from FR4. Also, I haven't found anybody in the states that will plug
vias with conductive epoxy on FR2 -- they'll plate it anyway. This can change your
RF significantly. Fab houses in the states would like you to use polyimide; me
too. But it's usually not a choice overseas and expect to keep the FOB cost down
to get it back here in the states (sorry, threw some purchasing lingo at ya). It's
up to the engineers to take of this problems in the circuits, and we can help by
providing a good RF layout.

Scott
IDS

Bob Landman wrote:

> 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]
> >