Hi Glenn! Don't have a real concrete answer for you, but as you probably already know, everything I've read recommends NSMD pads over SMD pads. I found figures of ball collapse that range from 20-25%, but those figures were all referencing NSMD pads. Sorry I couldn't be more help... But during my search, I found this excellent *.PDF file regarding PBGA's, covers just about everything... http://e-www.motorola.com/brdata/PDFDB/docs/PBGAPRES.pdf -Steve Gregory- > Technetters, > > There is a proposed design here that incorporates Solder Mask > Defined (SMD) and Non Solder Mask Defined (NSMD) BGA pads on the same part. > Solderable area on the pad is the same for both as is the solder ball > diameter to place. I'm concerned about coplanarity, but I don't have any > data to back it up. I know the SMD balls will be higher off the substrate > than the NSMD balls, but by how much? The reason for this design is > electrical performance. > > What do you think? Is the amount of variation in height too small > to be concerned about? > > Thanks, > > Glenn > --------------------------------------------------- Technet Mail List provided as a free 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------