Jack,
Thanks for your reply. The purpose of the board would be for 40+ Gbps
signals. Unfortunately at these speeds anything with glass weave starts
to affect the signals. The purpose for teflons is the loss tangents are
very very low and, depending on the material, there is little to no
glass weave.
(for Bill Brooks)
The last part of my statement about little to no glass weave is the
important part here that differentiates what we talked about a couple of
weeks ago.
For those that would like to know more.
The glass weave in laminates start to affect the signals at higher
frequencies say above 10 GHz. The reason has to do with the signal
traces and uniformity about the weave. The weave of the glass ebbs and
flows like a wave, meaning there are peaks and valleys. If one of the
signals of a differential pair were to be manufactured such that it
resides over more valleys than it does peaks, and the other signal was
over more peaks than valleys, the result would be that electrically at
high frequencies the signals would not be aligned (this is an
over-simplification of what is really going on). Even if the cad tool
routed them to within a mil, or 25um, of each other, they could still be
skewed significantly from a phase angle perspective. Why is this true?
The instantanious dielectric constant that the signals see would be
different. This causes the propagation velocity of the signal to be
different for the two traces. At low frequencies we assume that the
dielectric is uniform and therefore the dielectric constant is uniform,
at high frequencies this is not as true. The end result is that the
differential pair will have greater mode conversion, and there will be
additional attenuation of the signal as it propagates through the board.
This issue will need to be addressed during the design phase of a board
as signal frequencies continue to increase in speed.
Devon
========================================================================
Devon J. Post - C.I.D. Mayo Foundation
<mailto:[log in to unmask]> 200 First Street SW
Voice: (507) 538-5479 Sn 2-134C
Fax: (507) 284-9171 Rochester, MN 55905
Internet: http://www.mayo.edu/sppdg/sppdg_home_page.html
========================================================================
________________________________
From: Jack Olson [mailto:[log in to unmask]]
Sent: 14 March, 2007 9:29 PM
To: (Designers Council Forum); Post, Devon
Subject: Re: [DC] Information on multilayer boards with teflon materials
made using fusion bonding
You may already know this, but there are materials
with similar characteristics that are better suited to
multilayer constructions, if you can get away with it.
Maybe compare your needs to Rogers 4350?
We tried that on a previous project and it was good
enough for our 2.7GHz, and saved a ton of money too.
(My only experience with teflon is single-layer
circuits bonded to aluminum palettes, so I can't
help you with your real question.)
good luck,
Jack
On 3/13/07, Post, Devon <[log in to unmask]> wrote:
Does anyone have a contact or companies that they work with, and
are
willing to share, that can build a multilayer board out of
high-frequency teflon dielectrics using fusion bonding as their
lamination method for these dielectrics.
These would be research type boards with currently no mass
production
planned.
Devon
========================================================================
Devon J. Post - C.I.D. Mayo Foundation
<mailto:[log in to unmask]> 200 First
Street SW
Voice: (507) 538-5479 Sn 2-134C
Fax: (507) 284-9171 Rochester, MN
55905
Internet: http://www.mayo.edu/sppdg/sppdg_home_page.html
========================================================================
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