[SI-LIST] Re: Causes of Phase Differences in stripline construction

Hi Scott/All, 

As promised.

The material is Arlon 25N (Ceramic Thermoset). The cores are 2113. Ply is
dependent on thickness. 6 mil = 1-2113, 12 mil = 2-2113 etc. According to
the datasheet and manufacturing data provided by Arlon, the Dk @ 10GHz is
3.38 +/- 0.06, Df @ 10GHz is 0.0025

The prepregs are 2112 with ~ 71% Resin content. 

The phase measurement frequency is 1.3 GHz.

I also want to point out that this board has been manufactured for
approximately 3 years. As far as I know the phase delta issue started this
year. But I cannot definitively say whether the phase delta had always been
running < 8 degrees (the original spec). I have not been privy to that
information. We've been told the steady increase started occurring this year
and has pretty much stabilized around the max error of 15-18 degrees. Of
course this is not all assemblies, but the number of assemblies that have to
be tuned.

Thanks for all of the input so far.

Craig

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Scott McMorrow
Sent: Thursday, October 08, 2009 5:10 PM
To: Craig Sullivan
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Causes of Phase Differences in stripline construction

Craig

It would help to know what material is being used, and the frequency 
specified for measurement of phase delta.

Scott

-- 
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

TeraspeedR is the registered service mark of
Teraspeed Consulting Group LLC



Craig Sullivan wrote:
> Hello, 
>  
>
> I have a 2 part problem. Our customer has informed us they are seeing
phase
> errors in the assemblies we build for them. The requirement is all
channels
> need to have a phase delta of < 14.5 degrees. In other words, the max
phase
> - the min phase across 48 channels.
>
>  
>
> Part 1 of the problem is a phase delta in excess of 30 degrees. We have
> found the root cause of this problem to be PCB delamination.
>
>  
>
> Part 2 of the problem is the phase delta around 15-18 degrees. This is
> usually brought back into tolerance by changing an SMT capacitor. 
>
>  
>
> Finding the root cause of part 2 is proving to be rather challenging.
> Originally the specification was < 8 degrees. When the customer started
> seeing failures, they increased the specification to < 14.5. When they saw
> even more failures in addition to the delam, they finally brought it to
our
> attention. 
>
>  
>
> In my opinion the stripline construction "should" be rather forgiving.
It's
> 1/2 oz, 19.4 mils wide surrounded by ~18 mil dielectrics on each side.
> Though one of my concerns is each trace length is around 14.5 inches and
is
> serpentined. In addition, no two serpentine designs exhibit the exact same
> pattern. 
>
>  
>
> Another concern I have is the channels are spread across 3 different
layers
> in the stackup (16 channels each on layers 2, 7, and 11). The PCB is 12
> layers. 
>
>  
>
> Layers 2 and 11 have the same stackup:
>
> ==================== Ref
>
>      18 mil core
>
> -------------------- Signal
>
>      5.8 mil pp
>
>      6 mil core
>
>      5.8 mil pp
>
> ==================== Ref
>
>  
>
> Layer 7 is slightly different:
>
> ==================== Ref
>
>      12 mil core
>
>      5.8 mil pp
>
> -------------------- Signal
>
>      18 mil core
>
> ==================== Ref
>
>  
>
> Also to toss another variable in the mix. This board is completely round
> with each channel beginning at the perimeter of the PCB and equidistant
from
> the next channel. So with that said, I am aware of the trace orientation
in
> regard to weave/glass/resin now becomes a factor as well.
>
>  
>
> So my question to the list is: What are some causes of an increased phase
> spread? Also, any reference material recommendations are welcomed.
>
>  
>
> Thank you,
>
> Craig Sullivan
>
> Manufacturing Engineer
>
> MPL Incorporated
>
> P: 607.266.0480
>
> F: 607.266.0482
>
> csullivan@xxxxxxxxxx
>
>  
>
> Export Control:
> This message is intended only for the addressee and may contain
information
> that is company confidential or privileged.  Any technical data in this
> message may be exported only in accordance with the U.S. International
> Traffic in Arms Regulations (22 CFR Parts 120-130) or the Export
> Administration Regulations (15 CFR Parts 730-774). Unauthorized use is
> strictly prohibited and may be unlawful. If you are not the intended
> recipient, or the person responsible for delivering to the intended
> recipient, you should not read, copy, disclose or otherwise use this
> message. If you have received this email in error, please delete it, and
> advise the sender immediately. 
>
>  
>
>
>
> ------------------------------------------------------------------
> 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:
> http://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:     
>               http://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
>   
>
>
>   

------------------------------------------------------------------
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:
http://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:     
                http://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
  



------------------------------------------------------------------
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:
http://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:     
                http://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: