Hi, Eric If you think about it, a maximum will force the pad-edge to pad-edge spec to go out of tolerance, as the pitch must remain a minimum with respect to each other. That is why we all agreed a minimum pitch spacing was appropriate. Pad diameter has to remain within spec also. But I totally agree with the CpK approach; it should be applied to all of the attributes (pad diameter, connecting trace width, finished via diameter, copper thickness after etching, pitch, and co-planarity of finished copper pads. When you get into the business of performing ball attachment using automated processes with laser, you quickly realize just how much slop there is in the BGA industry. It has improved quite a bit due to the interaction with TI, Intel, Raytheon, etc, etc. Very little in the way of usable standards within JEDEC, especially for flipchips and CSPs. But that just underscores what you stated about the need for properly toleranced drawings. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Eric CHRISTISON Sent: Wednesday, May 20, 2009 3:08 AM To: [log in to unmask] Subject: Re: [TN] Strange Tolerances on BGA Pitch-How to Accomodate the Stencil File? So if there's no maximum am I right in assuming an actual pitch of 2mm would be acceptable :-)? In my view there's no excuse for poorly toleranced drawings, either ones with excessively slack tolerances or with missing information. The manufacturer should hae Cpk data ofr their pitch measurements which will allow them to quote a realistic tolerance. Regards, Stadem, Richard D. wrote: > While doing the laser ball attachment on other BGAs, the company that did it noted that there was up to a +- 3 mil deviation in the pitch in earlier revisions of various BGA substrate drawings, so we asked for a tighter spec for the center-to-center distance from the BGA substrate fabricators because the laser is very precise and it is faster when the machine does not have to autocorrect frequently. So instead of a standard 1mm [.040"] with no tolerance (as an example), it became 1mm [.040"] minimum to ensure no two pads were less than that from each other, center-to-center. It should not affect your stencil file, in fact it should help ensure your stencil artwork will be properly aligned by ensuring less of a stackup variation in the artwork, the pad locations on the BGA substrate, and the pad locations on the PWB substrate. This was carried over to other BGA fabricators as well. If you check other BGA drawings you will note the same wording. This is then flowed down to the PWB design requirements, provided the CID diligently notes the artwork requirements when specifying the BGA artwork on his/her PWB. > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of bob wettermann > Sent: Tuesday, May 19, 2009 7:44 AM > To: [log in to unmask] > Subject: [TN] Strange Tolerances on BGA Pitch-How to Accomodate the Stencil File? > > In working with some newer Intel BGA datasheets we > Dear Technetters: > > In working with some newer Intel BGA datasheets we are noting tht the pitch is indicated as a minimum dimension. For instance on a current job the spec indicates "Min 1mm". Has anyone else seen this trend? Explanations? > > How are you acoomodating your stencil files? > > Regards > Bob Wettermann > PH 847-767-5745 > > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV 15.0 > 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 15.0 > 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 > ----------------------------------------------------- > > -- Eric Christison Msc Mechanical Engineer Consumer & Micro group Imaging Division STMicroelectronics (R&D) Ltd 33 Pinkhill Edinburgh EH12 7BF United Kingdom Tel: +44 (0)131 336 6165 Fax: + 44 (0)131 336 6001 --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 15.0 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 -----------------------------------------------------