Paul - Once upon a time in a previous life I had the occasion to be involved in a similar effort. We learned a bunch of stuff that does and doesn't work and ultimately developed two approaches that were worthwhile: 1] Riser wires soldered, sequentially into the boards, with the boards being spaced about .06" inches apart. The separation distance allowed sufficient heat dissipation to prevent reflow or melt of the preceeding solder connections. TCE of the spacers used to mount the boards needs to be a reasonable match to that of the riser wires to prevent setting up a solder fatigue risk. We reached a maximum stack up of about 6 boards/cables on this application; 2] Installation of "cage jacks" in plated thru holes in the boards, followed by installation of riser wires (non-soldered) at time of board to board assembly. Riser wires and contact areas of cage jacks were Au plated. Cage jacks were supplied on headers which also served to prevent entry of solvents/flux/etc., during processing. We reached a maximum stack up of 10 boards on this approach. Both of these design approaches were ultimately space qualified for USAF and NASA applications. Regards - Kelly ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################