[SI-LIST] Re: High-Speed (coax) PCB Connector Transitions -- selection, PCB footprint, and performance

  • From: "Barnes, Heidi" <heidi.barnes@xxxxxxxxxx>
  • To: <wolfgang.maichen@xxxxxxxxxxxx>
  • Date: Mon, 9 Mar 2009 21:42:04 -0500

Hi Wolfgang,
I use the 5mil pin that steps to 8 mils and then pull it forward until the 
stepped edge lines up with the overhang on the connector (Southwest confirmed 
that there is plenty of pin length internal to the connector to do this), the 
larger diameter hitting the board edge adds a bit more pressure for the pin 
contacting the board, makes it easier to visually align since the pin sticks 
out further, and a bit of a capacitive stub right at the board edge doesn't 
seem to hurt.  Also, I shouldn't admit it... but I use the backing piece from 
the Rosenberger connectors since it uses a slightly more robust screw that can 
handle the 250 mil + ATE Loadboards and I can use the Torx head with them so 
they don't strip quite so fast. 
 
Connectors are always a bit of an art at high speeds...
-Heidi
________________________________

From: wolfgang.maichen@xxxxxxxxxxxx [mailto:wolfgang.maichen@xxxxxxxxxxxx] 
Sent: Monday, March 09, 2009 5:08 PM
To: Barnes, Heidi
Cc: Michael Rodrigues; si-list@xxxxxxxxxxxxx; si-list-bounce@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: High-Speed (coax) PCB Connector Transitions -- 
selection, PCB footprint, and performance



I would second the recommendation for the Southwest Microwave edge launch 
connectors. A bit on the pricey side, but that gets compensated by the fact 
that you can re-use them easily since they are press-fit (only screwed down, 
not soldered). The only issue I had with them was out of some reason with 
thicker boards (over 100 mils) sometimes the center conductor would not make 
contact and I had to manually bend it downwards slightly (VERY carefully 
because it is thin and fragile). Otherwise, performance is great - of course 
you need take great care with the board (trace) layout & landing pattern / vias 
in order to get the most out of the connector. Southwest has a few standard 
landing patterns available on demand. 

Rosenberger works well, too, and with a bit of luck and carefulness you can 
desolder an re-use them, too (that usually takes two peope, one unscrewing and 
holding the connector, and one operating the heat gun, otherwise you'll break 
off the fragile center connector). 

Wolfgang 





"Barnes, Heidi" <heidi.barnes@xxxxxxxxxx> 
Sent by: si-list-bounce@xxxxxxxxxxxxx 

03/09/2009 02:00 PM 

To
"Michael Rodrigues" <michael.rodrigues@xxxxxxxxxx> 
cc
<si-list@xxxxxxxxxxxxx> 
Subject
[SI-LIST] Re: High-Speed (coax) PCB Connector Transitions -- selection, PCB 
footprint, and performance

        




I prefer the Southwest 2.4mm since it just clamps to the PCB, can easilby be 
re-adjusted if mis-aligned and is re-usable.  Also the pins are replaceable and 
SMA versions are available.  The footprint is interchangeable with the 
Rosenberger 09K243-40ME3 if one needs a permenant soldered connection.  Let me 
know if you need the footprint I am using which is different from the Southwest 
data sheet and closer to what Rosenberger has for their connector.

Molex has a lower performance clamped on verticle SMA connector that may 
provide more mounting flexibility if you need it...Molex used it for a 
DesignCon paper in 2006 "Practical Design and Implementation of Stripline TRL 
Calibration Fixtures for 10-Gigabit Interconnect Analysis" 
http://www.designcon.com/infovault/paper.asp?PAPER_ID!9  They may have made 
improvements in the footprint since then.


Regards,
Heidi Barnes





-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On 
Behalf Of Michael Rodrigues
Sent: Monday, March 09, 2009 10:51 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] High-Speed (coax) PCB Connector Transitions -- selection, 
PCB footprint, and performance

Hello all at SI-List,


I am trying to implement a PCB connector transition board for the purpose of 
measuring a structure at up to 20 GHz. I would be interested in using the best 
performing coax-to-PCB launch I can find so that it will not contribute losses 
to the actual structure losses I am interested in measuring (i.e., it will be 
invisible to the measurement, or as much so as possible).



Two questions I have would be:

1)       What would be the best connector type for this purpose (i.e.,
interfacing to VNA and high-speed o-scopes for s-parameter, TDR, and TDT 
measurements)?

2)       How important is the PCB footprint for the connector; what
would be the best way to make sure you are using the best footprint possible 
(assuming the case where PCB footprint for a PCB connector are not a 
no-brainer)?



Some connectors I have been looking at would include:



2.4 mm (DC to 50 GHz):

*                 Rosenberger 09K243-40ME3
*                 Southwest 1493-03A-5





Mini-SMP (DC to 65 GHz):

*                 Rosenberger 18 S 203- 40M L5 
*                 Rosenberger 18 S 102- 40M L5



Thank you in advance for any replies.



Best regards,

Michael



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