You end up with twice the power on the same footprint which can be an issue in some cases, also since they are occupying the same X Y space it is almost (but not quite!!) impossible to do re-work on one device without driving the other into secondary reflow. John John Burke Senior Manager - Operations , Optichron [log in to unmask] W: 510 249 5233 M: 408 515 4992 http://www.optichron.com Profile: https://www.linkedin.com/e/fps/2665502/ -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Tempea, Ioan Sent: Friday, March 24, 2006 6:30 AM To: [log in to unmask] Subject: [TN] Superposed BGAs Hi Technos, I am reviewing have a PCB design draft which has 2 MEG-Array BGA connectors from FCI. The problem is that one is on the topside and the second one on the bottom side, their locations perfectly overlapping. Otherwise said they one on top of the other. I remember having seen a thread on Technet a few years ago stating that this construction is not reliable. Unfortunately I cannot find the e-mails in the archive. What would be your take on this? Thank you, Ioan --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------