Don't ask what the designers prefer, ask what the customers (users) prefer. The most common size/shape is a 1mm (0.040") circle. It is prefered to have a flat finish, so that the vision cameras do not get confused by variations in reflections and glare. That is also why solder mask is not put up to the edge of the fiducial. Any error in putting down the solder mask will cover part of the fiducial. Have fun, Ahne. Fine Line Stencil, Inc. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas McCall Sent: Wednesday, 04 June, 2008 03:14 To: [log in to unmask] Subject: [TN] Fiducial solder resist clearance Hi, When desiging the PWB for fiducials, what is the experience of having the solder resist up to the edge of the fiducial pad. If the recommended clearance window round (2-3 x fiducial radius) the fiducial is not maintained does this in general cause excessive vision system problems, - looking at the solder resist compared to looking at the laminate material. I understand that this clearance should be left with no resist and leaving the bare PWB laminate and etched fidicial feature. What is the prefered fiducial shape used by most designers? Thanks in advance for any information. D. McCall. _________________________________________________________________ Great deals on almost anything at eBay.co.uk. Search, bid, find and win on eBay today! http://clk.atdmt.com/UKM/go/msnnkmgl0010000004ukm/direct/01/ --------------------------------------------------- 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 -----------------------------------------------------