Steve, This might be a case where a note on the fab drawing stating "Soldermask must be aligned to outer layer features +/-.002 inch" or something to that effect would help you. Course, you better check that the fab house is comfortable signing up to that spec, or you better let them micromodify the SMASK openings around any BGAs to give added clearance. Not sure what to do about boards "as received" without any preexisting notes on the drawing. Hal -----Original Message----- From: Stephen Gregory [mailto:[log in to unmask]] Sent: Tuesday, August 02, 2005 1:33 PM To: [log in to unmask] Subject: [TN] Soldermask registration for NSMD BGA pads... Afternoon All! Just sitting down for lunch, and I have a question about Non Solder Mask Defined (NSMD) BGA pads. I have a picture at: http://www.stevezeva.homestead.com/files/MaskMisregistration2.jpg Now according to IPC-A-600G, that misregistration is not rejectable, "because the solder resist does not encroach on the land except at the conductor attachment"...that's a quote right out of the - 600. I've looked at it very closely, the mask is right up against edge of the pad. Knowing what kind of solder joint you're trying to acheive with a NSMD pad, and having the mask up against the edge of the pad, the solder is not going to wet and flow down around pad like you want, right? Is that a problem? Will that introduce the possibilty for reliability issues? Can one reject these boards? I've heard the statement made that if indeed you want a clear area around the pad, a note needs to be put on the fab drawing stating that. Because as it stands now according to the IPC-A-600G, it is not rejectable. Any thoughts? Kind regards, -Steve Gregory- Senior Process Engineer LaBarge Incorporated Tulsa, Oklahoma (918) 459-2285 (918) 459-2350 FAX __________________________________________________________________ This message may contain information that is privileged and confidential to LaBarge, Inc. It is for use only by the individual or entity named above. If you are not the intended recipient, you may not copy, use or deliver this message to anyone. In such event, you should destroy the message and kindly notify the sender by reply e-mail. --------------------------------------------------- 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 -----------------------------------------------------