Dennis - thanks for sending me your attachment separately. The ground-plane flooding on layer 1 that your EE wants will result in BGA solder ball pads that are defined by the soldermask opening. More than 10 years ago, Motorola and other companies went thru quite a bit of thermal-cycling testing and found that this design (dubbed "captured pads") causes solder joint fatigue and failure faster than non-captured pads. Basically, captured pads create a hi-stress-concentration area in the solder joint that is more susceptible to creep and failure due to the differences in thermal expansion between the PC board and the BGA package (which is dominated by the die bonded to it in the 'shadow' of the die). To address your concern on assembly, I'm not aware of any studies (and would not think) that a flooded plane would cause assembly problems. Good luck - EEs can be hard to deal with. Terri (an EE) -----Original Message----- From: Denis Lefebvre [mailto:[log in to unmask]] Sent: Thursday, May 23, 2002 10:10 AM To: [log in to unmask] Subject: [TN] BGA Solderability Technet; As a designer, I diligently try to understand and account for fabrication and assembly issues in my designs. It can be frustrating when working with EE's that are not well versed in manufacturing as they request things that you know are not good practice from a DFM viewpoint. I have a case now where an EE is asking for a copper fill on BGA ground pins. Since this is not easy to describe in a way that every one can understand, I am including a small JPG to illustrate. It is a 356 pin BGA, 1mm pitch, 0.5mm solder lands. I am convinced that this will not fare well when they try to solder this part, yet the engineer insists on doing it this way. What argument can I make, with supporting data, to persuade him? Simply telling him that I know it is poor practice isn't cutting it! [Adjusting tie..."I tell ya, we get no respect!"] Denis Lefebvre, C.I.D. Senior PCB Designer 408-542-3832 Finisar Corporation 1308 Moffett Park Drive Sunnyvale, CA 94086 www.finisar.com <http://www.finisar.com/> --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------