Vince Harlan asked:
     
>     I have a 12 layer PWB(Backplane) with 8 ground planes(all 2 oz.). 
>     Each connector on this assembly has several pins that connect to 
>     all 8 ground planes.  Each connection is thermally relieved by 4 
>     separate .010" traces(spoked).  Each trace is .035" in length.

>     The connectors that are on the top layer have been successfully 
>     flowsoldered, ...
     
>     Does anyone have experience with this type of design and/or are 
>     there any guidelines that might help me in reevaluating this 


	Most interesting...  These values are roughly 4x the maximums
	for IPC-D-275 on thermal reliefs.  On *several* occaisions I've
	been faced with higher current levels than the IPC std would per-
	mit, and have needed to specify hand soldering since I could not
	get reassurance (on technet or otherwise) that reliable machine
	soldering was possible.

	Perhaps it's the .035" long hookup that helps?

	Perhaps it's also time to look at IPC-D-275's thermal relief spec-
	ification.  Can anyone comment on the origins of that spec?

	Best regards,

        Jeff Seeger                             Applied CAD Knowledge Inc
        Chief Technical Officer                      Tyngsboro, MA  01879
        [log in to unmask]                               508 649 9800

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