[SI-LIST] Re: backplane connector

In my opinion, this is almost like asking "Which is better, red wine or
white wine?"  Both have their advantages and disadvantages in various
applications. 

Surface mount can most definitely offer some electrical advantages.  If you
keep your vias under control, routing options on inner layers are much more
flexible with surface mount connectors.  Surface mount also allows you to
use stopped or drilled via technologies to eliminate stub effects.  With
press fit, you need full length vias. 

There are some different mechanical challenges associated with surface mount
connectors.  Probably the most significant is in trying to maintain
acceptable coplanarity in the terminals across a large connector.
Coplanarity is important in reflow processing.  Thermal expansion of the
board vs the connector is another concern.  And sometimes additional means
of mechanical support might be required for surface mount versions.  The
press fit connectors tend to be much more rugged, as-is. 


 
-----Original Message-----
From: Dr. Howard Johnson [mailto:howiej@xxxxxxxxxx]
Sent: Wednesday, March 27, 2002 12:02 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] backplane connector



I'm doing some research for an EDN column about the use of
surface-mounted backplane
connectors as opposed to press-fit types for high-speed
serial backplanes (in the
GHz+ speed range).

Of course the press-fit conectors have the advantage of not
requiring soldering on
your backplane, which means you can incorporate cheezy
plastic parts into the connector
shells.

The surface-mounted connectors work well with very small
blind
vias which are good for high-speed signals.

Which is best? Where are we going in the future?

Any comments you would care to submit to my attention (
howiej@xxxxxxxxxx ) or post
here on the si-list would be greatly appreciated. Please
include the words:
"backplane connector" in the subject line to make sure I see
the message.


Best regards,
Dr. Howard Johnson, Signal Consulting Inc.,
tel +1 509-997-0505,  howiej@xxxxxxxxxx
http:\\sigcon.com  -- High-Speed Digital Design articles,
books, tools, and seminars

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