FreeLists / si-list / [SI-LIST] Re: How to properly simulate signal integrity across PCBs interconnected by Flex?

["Kotson, Michael" <mkotson@xxxxxxxxxxx>]

Hi Jean-Pierre,
   We regularly use flex cables in our designs which must be qualified
for MIL-STD EMI levels (much tougher than FCC), so I really don't think
you will have much issue.  Follow the same design guidelines that you
would for a rigid PCB (continuous return path, minimize reflections,
etc).  Samtec does a great job of providing spice connector models for
flex-type connectors.  Most any simulation package will handle this kind
of scenario, but I personally use Hyperlynx due to its simplicity.  One
word of caution however, polyimide (the dielectric used to make flex
circuits) can be _VERY_ lossy at higher frequencies.  Always check the
loss tangent of the polyimide manufacturer you plan to use, as I've seen
a wide range in this number from various manufacturers.

Best of luck to you,
-Mike

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of jeanpierrepoulin
Sent: Friday, August 31, 2007 2:04 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] How to properly simulate signal integrity across PCBs
interconnected by Flex?

Hello Gurus,

I am attempting to correctly design the first time a system=20
consisting of five small PCBs interconnected by short (1-5 inch) Flex=20
cable.  While most signals are single ended and of moderate speed (20-
80 Mhz and with most edges controlled by the driving strength of FPGA=20
drivers), I am particularly concerned about some clock signals that I=20
need to spread to all these PCBs and wish to properly simulate...

1. Is there a flex connector vendor in particular that publishes=20
quality IBIS model the simulating software will need?

2. What simulating software do you recommend as easiest to use for=20
this type of need?

3. Do you think usage of Flex cabling in this fashion would cause =20
problems during FCC certification?

4. Any good web site / publication you've seen on the subject of=20
signal integrity across Flex cabling?

Any hint you could offer is greatly appreciated!!

   Jean-Pierre Poulin


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