[SI-LIST] Re: AW: Multi-Giga-Hertz Rigid-Flex Feasibility

  • From: Hirshtal Itzhak <ihirshtal@xxxxxxxxxx>
  • To: Scott McMorrow <scott@xxxxxxxxxxxxx>, Lee Ritchey <leeritchey@xxxxxxxxxxxxx>
  • Date: Wed, 02 Dec 2009 11:37:13 +0200

Hi Scott
 

As I've already told a few times in my emails, my main concern is impedance 
continuity across the rigid-flex-rigid combination.

 

If the tolerance of the 3 sections is independent of each other, and if the 
flex tolerance is +/-20%, assuming a standard +/-10% tolerance on the rigid 
boards, this could create a substantial impedance discontinuity, e.g: 120-Ohm 
on the Flex and 90-Ohm on the Rigids.

 

I just wanted to know if and how it's practical, and over what flex-length, to 
transfer a few GHz (up to 3.125GHz) signals from one rigid board to the other

 

Thanks

 

Itzhak  

 

________________________________

From: Scott McMorrow [mailto:scott@xxxxxxxxxxxxx] 
Sent: Tuesday, December 01, 2009 4:05 PM
To: Lee Ritchey
Cc: Hirshtal Itzhak; Gert Havermann; si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: AW: Multi-Giga-Hertz Rigid-Flex Feasibility

 

I agree with Lee, microstrip works just fine for flex circuits with a cover 
layer.  High performance stripline is also achievable in a flexible assembly if 
you crosshatch the planes.  To do this, you need to do a bit of engineering 
homework in order to achieve controlled impedance and low loss.

scott


Lee Ritchey wrote: 

Itzhtal,
 
I use both polyamide based flex material and Liquid Crystal Polymer from
Rogers.  Both work well.  LCP has lower loss.
 
The reason that stripline is usually not used in flex circuits is that
makes a 3 layer assembly which is not very flexible.  There is nothing
wrong with microstrip.  Works fine.
 
Lee Ritchey
 
 
 
 
  

        [Original Message]
        From: Hirshtal Itzhak <ihirshtal@xxxxxxxxxx> 
<mailto:ihirshtal@xxxxxxxxxx> 
        To: Havermann, Gert <Gert.Havermann@xxxxxxxxxxx> 
<mailto:Gert.Havermann@xxxxxxxxxxx> ; <si-list@xxxxxxxxxxxxx> 
<mailto:si-list@xxxxxxxxxxxxx> 
        Date: 11/29/2009 4:00:51 AM
        Subject: [SI-LIST] Re: AW: Multi-Giga-Hertz Rigid-Flex Feasibility
         
        Hello Gert
         
        First - thank you for your contribution.
         
        I have a few questions regarding your email:
         
        1) You refer to a trace width of 0.8mm as "small". This is a 31.5mil
            

width, which I hardly call "small"! I regularly use 3-4 mil trace widths in
my designs. Is there something different in Flex circuits, which enforces
me to use such LARGE traces (compared to my regular traces)?
  

        2) I see the problem you mention for the Microstrip configuration. Is it
            

common to use Stripline on a flex circuit? I was told this is impractical,
although I'm not sure what the reason is.
  

        Thanks
         
        Itzhak Hirshtal
        Elta
         
        -----Original Message-----
        From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
            

On Behalf Of Havermann, Gert
  

        Sent: Tuesday, November 24, 2009 4:19 PM
        To: si-list@xxxxxxxxxxxxx
        Subject: [SI-LIST] AW: Multi-Giga-Hertz Rigid-Flex Feasibility
         
        Hello Itzhak ,
         
        All Polimide (Kapton) materials will do the job from a loss and
            

dispersion prospective. The tolerance you mention seems to be unreasonable
high for an etching tolerance. I did Flex designs with impedance control,
100Ohm +/-10Ohm, 0.8mm tracewidth without problems (of corse I had to pay
extra for the small trace width). 
  

        If you refer to an impedance tolerance due to bending and surrounding
            

material, thats another story. If you design it in microstrip (as you are
planning it), then  everithing touching the flex might change your
impedance. Designing it in stripline decreases the flexibility of the flex
and increases cost.
  

        Look for Dupont, Grace Electron or Shengyi Flex materials for more info.
         
        BR
        Gert
         
         
        
--------------------------------------------------------------------------
        Absender ist HARTING Electronics GmbH & Co. KG; Sitz der Gesellschaft:
            

Espelkamp; Registergericht: Bad Oeynhausen; Register-Nr.: HRA 5596;
persönlich haftende Gesellschafterin: HARTING Electronics Management GmbH;
Sitz der Komplementär-GmbH: Espelkamp; Registergericht der
Komplementär-GmbH: Bad Oeynhausen; Register-Nr. der Komplementär-GmbH: HRB
8808; Geschäftsführer: Torsten Ratzmann
  

        -----Ursprüngliche Nachricht-----
         
        Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
            

Im Auftrag von Hirshtal Itzhak
  

        Gesendet: Dienstag, 24. November 2009 14:21
        An: si-list@xxxxxxxxxxxxx
        Betreff: [SI-LIST] Multi-Giga-Hertz Rigid-Flex Feasibility
         
        Hello All
         
         
        My project manager intends to use a rigid-flex design in our next
            

high-speed board.
  

         
         
        He wants to route a few pairs of 3.125GHz from a rigid section to 
another
            

one through a flex section.
  

         
         
        Does anyone know if this is feasible? I found out that the 2 sections,
            

although spec'd to be 100-Ohm diff impedance, can still differ
substantially - as much as 30%, because the tolerance of the flex section
is +/-20%. Can such a design work for a substantial trace length? Should I
restrict the trace length on the flex section to be no more than an inch or
so, in order to reduce the impact of the supposed non-uniform impedance?
  

         
         
        I intend to use a 2-layer flexible laminate with the pairs on one layer
            

and a Ground reference on the other one.
  

         
         
        Any advice on this matter would be helpful
         
         
         
        Thanks
         
         
         
        Itzhak hirshtal
         
         
         
         
         
         The information contained in this communication is proprietary to 
Israel
            

Aerospace Industries Ltd., ELTA Systems Ltd. 
  

        and/or third parties, may contain classified or privileged information,
            

and is intended only for the use of the intended addressee thereof. If you
are not the intended addressee, please be aware that any use, disclosure,
distribution and/or copying of this communication is strictly prohibited.
  

        If you receive this communication in error, please notify the sender
            

immediately and delete it from your computer. Thank you. 
  

         
        This message is processed by the PrivaWall Email Security Server. 
         
         
         
         
        ------------------------------------------------------------------
        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
         
        Old (prior to June 6, 2001) list archives are viewable at:
                 http://www.qsl.net/wb6tpu
          
         
         
         
        http://www.mesago.de/de/SPS/main.htm
        Besuchen Sie uns auf der SPS/IPC/Drives 2009 
        vom 24. - 26. November 2009 in Nürnberg, in Halle 10 am Stand 130.
         
        ------------------------------------------------------------------
        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
         
        Old (prior to June 6, 2001) list archives are viewable at:
                 http://www.qsl.net/wb6tpu
          
         
         
        This message is processed by the PrivaWall Email Security Server. 
         
         
         
         
         The information contained in this communication is proprietary to 
Israel
            

Aerospace Industries Ltd., ELTA Systems Ltd. 
  

        and/or third parties, may contain classified or privileged information,
            

and is intended only for 
  

        the use of the intended addressee thereof. If you are not the intended
            

addressee, please be aware 
  

        that any use, disclosure, distribution and/or copying of this
            

communication is strictly prohibited.
  

        If you receive this communication in error, please notify the sender
            

immediately and delete it from 
  

        your computer. Thank you. 
         
         
        This message is processed by the PrivaWall Email Security Server. 
         
         
         
        ------------------------------------------------------------------
        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
         
        Old (prior to June 6, 2001) list archives are viewable at:
                 http://www.qsl.net/wb6tpu
          
            

 
 
------------------------------------------------------------------
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
 
Old (prior to June 6, 2001) list archives are viewable at:
               http://www.qsl.net/wb6tpu
  
 
 
  





-- 
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
 
http://www.teraspeed.com
 
Teraspeed® is the registered service mark of
Teraspeed Consulting Group LLC



This message is processed by the PrivaWall Email Security Server. 



 The information contained in this communication is proprietary to Israel 
Aerospace Industries Ltd., ELTA Systems Ltd. 
and/or third parties, may contain classified or privileged information, and is 
intended only for 
the use of the intended addressee thereof. If you are not the intended 
addressee, please be aware 
that any use, disclosure, distribution and/or copying of this communication is 
strictly prohibited.
If you receive this communication in error, please notify the sender 
immediately and delete it from 
your computer. Thank you. 


This message is processed by the PrivaWall Email Security Server. 



------------------------------------------------------------------
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
 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  

Other related posts: