[SI-LIST] Re: Are flex pcbs now competing with ribbon calbes in terms of signal integrity?

  • From: "Julian Ferry" <julian.ferry@xxxxxxxxxx>
  • To: <rdudek@xxxxxxxxxxxxxxx>, <tom_cip_11551@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
  • Date: Thu, 8 Nov 2007 15:03:13 -0500

Reel-to-reel processes are also available which allow extremely long
(100 meter +) flex runs to be fabricated, so the panel size limitation
goes away.  Here's an example.

http://www.flexiblecircuits.co.uk/products/reel_to_reel.asp


At Samtec, we manufacture both high speed ribbon assemblies and high
speed flex assemblies.=20

http://www.samtec.com/flex_circuitry/Flex_standard_HS.aspx?nav=3D1760


http://www.samtec.com/cable_assemblies/data_rate/std_drc.aspx?nav=3D1754


Both have their pros and cons, and it is often a tough call as to which
is best suited for a particular application. =20

For short runs (< 2 feet), flex can make a lot of sense.  But for longer
runs, coax or twinax ribbon cables can offer lower loss.  And cable is
better at handling higher power levels.

Flex can definitely work in high speed applications, but a lot of folks
just don't seem to think about it that way.  We're actually using flex
assemblies in RF and microwave applications where coax was once
considered mandatory.

In making the choice between flex and cable, mechanical requirements
often win out over electrical.  Flex is usually lighter and smaller. And
it can offer much better flex-life performance, but usually in only one
axis of flexing.  Cable can offer better flexibility in all 3 axes.



Julian Ferry
High Speed Engineering Manager
Samtec, Inc

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Russell Dudek
Sent: Thursday, November 08, 2007 2:06 PM
To: tom_cip_11551@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Are flex pcbs now competing with ribbon calbes in
terms of signal integrity?

Hi Tom,

This is the "origami" approach to getting a long flex out of a
manufactures
standard panel size.  This requires one to step outside of the typical
2D
panel space and to start folding in 3D.  The serpentine, as shown below,
can
be stretched rather far limited only be the width of the flex circuit.
Actually as the flex width approaches zero, it can be stretched to
infinity...Hope this helps...

 _   _
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| |_| |
  =20

Russell


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On
Behalf Of tom_cip_11551
Sent: Thursday, November 08, 2007 1:16 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Are flex pcbs now competing with ribbon calbes in
terms
of signal integrity?

Hi Si-List experts,

I am working on an application that requres ribbon cable runs of=20
about a meter, for differential pairs at 100 Ohms (50 Ohms odd mode)=20
impedance. My data rate is about 1.5 Gb/s . I have had lots of=20
experience specifying printed circuit boards over the years and I=20
though that "flex" pcb circuits were limited to the panel sizes of a=20
particular fab house. Recently, I have seen some data to the effect=20
that "ribbons", manufactured like pcbs,  are available now that can=20
be run for many feet, because of "step and repeat" fabrication=20
processes.=20

Yes, I am aware of the limiting factors of long cable runs on high=20
speed signals (dispersion, crosstalk, emi, etc) but I am wondering if=20
FPC (flexible printed circuit) technology has advanced to the point=20
where it can compete with ribbon cable technologies. I know that in=20
terms of signal integrity, a pcb beats a cable.

Thank You
Tom
tom_cip_11551@xxxxxxxxxxx



------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List technical documents are available at:
                http://www.si-list.net

List archives are viewable at:    =20
                //www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
 =20



------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List technical documents are available at:
                http://www.si-list.net

List archives are viewable at:    =20
                //www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
 =20

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List technical documents are available at:
                http://www.si-list.net

List archives are viewable at:     
                //www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  

Other related posts: