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June 1998

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Subject:
From:
Mitch Morey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 2 Jun 1998 09:54:38 -0700
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Art,

First, thank you so much for following this thread on Hi-Freq materials
and giving us the suppliers information.

I have been working with these issues the last couple weeks and want
to give some input I've collected.

I hear very good things about Rogers material, and have no complaints
with using it, if necessary. But, some info has crossed my hands, and I'm
not sure I have need for what Rogers can give me, for a cost $$.

I had a couple board manufactures in here, and the rep from GE (makers
of Getek material. The fab shops have no qualms using Getek, and the
costs are very much in line with FR4 material processing. Maybe 15-20%
more per lot. But, I have published data from GE concerning Getek
material up to 12Ghz. And, they supply a spreadsheet so you can
calculate your own stackups, with whatever frequencies you use to
give you your impedance values. With this, I can do my 2Ghz design on
Getek material, and quite possibly acheive +/- 2% tolerance! They also
market an impedance "simulator" which goes WAY beyond any
impedance "calculator" I've seen available. By simulator I mean it will
simulator all the factors effecting your stackup, not just layer to layer! I'm
working to purchase it ASAP. It's very impressive.

Now, for costs... From what I could gather Getek material ($4.07) is not
quite 2X as much as FR4 material (~$2.75 for .021 core material), and
Rogers 4003 material ($9.95) is not quite 4X FR4 material. These values
are disputable, as they will change from supplier to supplier, and from
quantity to quantity, but those are value we currently look at.

As I said, I like all these materials, for whatever application they apply to,
but at 2Ghz (and any impedance designs, now) I'll use the Getek
material. If it doesn't work, I'll surely go back online and bitch.

Thanks again Art.  :)

Mitch Morey
Sr PCB Designer
NSI Communications
San Diego
(619)657-5338

>>> "Arturo J. Aguayo" <[log in to unmask]> 06/02/98 07:12am
>>>
Frank,

You are correct in that each application is different and one can use
FR4 in some applications greater than 1 GHz. Loss is an important
factor, but we have seen designers switch from FR4 to a high
frequency
material because of dielectric tolerance too. That I'm aware of, there
is no tolerance (or at least published) in dielectric tolerance for FR4
or many other high Tg materials, only on those designed specifically for
RF/microwave applications. Because of that fact, some FR4 boards
require
much tuning to get them to work, this adds overall cost to the finished
circuit and in some cases it is cheaper to got to a more expensive
laminate and eliminate tuning. Each application is different and if I
were desining a board I would give FR4 a shot also. Let's face it, if it
works after looking at all costs then there is nothing that somebody
like me (working for a supplier of high frequency laminates) can say to
convince you to switch away from FR4 (but there are cases down to
500
MHz, digital, where the change has happened).

regards
Art Aguayo
[log in to unmask]
www.rogers-corp.com/mwu/
[log in to unmask] wrote:

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