Ashok, I typically see 1-2 mil over-etch, but that is on 1/2 oz copper and I am guessing that no adjustments have been made from the gerber data prior to fabrication. I would assume that 1 oz or 2 oz copper would have even more etch, and that you (your board vendor) would need to start adjusting for the etch. Ben -----Original Message----- From: Ashok Dhawan [mailto:[log in to unmask]] Sent: Monday, May 19, 2008 9:23 AM To: TechNet E-Mail Forum; Gumpert, Ben; [log in to unmask] Subject: RE: [TN] Solder Pad width Importance: High Ben It is not that simple as you do not start with 20 mils pad. There is provision for etching which varies. I was looking for actual pad width measured on production boards at 20 mil pitch TSOP or QFPs if someone is using 2 Ozs copper. Interestingly, cross-section of Pad is not rectangular in shape. It is more like trapezoid. Topside is narrow and base is wide. For printing, topside of the pad is relevant surface for gasketing with stencil apertures. I will appreciate your experience in measured data (topside of pad) regards Ashok Dhawan Manufacturing Engineer Parker Hanniffin Inc Winnipeg Canada -----Original Message----- From: TechNet on behalf of Gumpert, Ben Sent: Mon 5/19/2008 8:00 AM To: [log in to unmask] Subject: Re: [TN] Solder Pad width Ashok, Looks like you answered your own question. 20 mil pad design - (2.5 mil etch x 2 sides) = 15 mil pad actual > 10 mils Ben -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Ashok Dhawan Sent: Thursday, May 15, 2008 9:05 PM To: [log in to unmask] Subject: [TN] Solder Pad width I am looking for measured pad width for 20 mil land pattern for SMT. (QFP or TSOP) What is Pad width actal versus top copper layer? Copper outer layer is 1 oz or 2 oz or 3 ozs. Reason for this question: Stencil is 6mils thick with min aperture opening of 9 mils. For gasketing, the pad need to o=be over 10 mils. 2 Ozs copper has etch factor 2.5 mils over etch each side. Can final pad width of over 10 mils be made. Any inputs on this will be appreciated. Regards Ashok --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------