Perhaps the requirement is for thermal relief during soldering. They may have encountered a problem soldering to a SMT pad with a large trace acting as a heat sink. Jim Marsico ITT Corporation 1500 New Horizons Blvd. North Amityville, NY 11701 631-630-5079 [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Upton, Shawn Sent: Tuesday, January 11, 2011 1:28 PM To: [log in to unmask] Subject: Re: [TN] Trace Widths Entering SMT Ah, well that is something different--if it predates, and must be followed, well, you're stuck most likely, unless if you want it to be your neck if you attempt otherwise. If you want to have fun with him, ask how far away the necking down of a trace is--for instance, let's say you wanted a 50mil trace to the pad, how far away do you have to neck down to 20mil? IOW, how long is the minimum 20mil trace length from the pad supposed to be? The rule doesn't make sense to me, but I only deal with low volume stuff. I did have one board house tell me that I didn't need thermal reliefs on a rather large SMT pad! [It was a small, low volume board though.] I haven't run into a problem with assembly houses and "too thick" traces, other than if I need to have a board reworked once we got it back (blew something up in the lab, let's say). Then those thermal reliefs matter--but a 50mil wide trace is hardly that much of a conductor of heat... Shawn Upton, KB1CKT Test Engineer Allegro MicroSystems, Inc [log in to unmask] 603.626.2429/fax: 603.641.5336 -----Original Message----- From: Cote, Clint (GE Intelligent Platforms, US) [mailto:[log in to unmask]] Sent: Tuesday, January 11, 2011 1:21 PM To: Upton, Shawn; TechNet E-Mail Forum Subject: RE: [TN] Trace Widths Entering SMT Yes, standard FR4 multi-layer with soldermask. I asked the Engineer and he isn't sure because the requirement pre-dates him. But, he is adamant that the requirement must be met. ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- 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.aspx?Pageid=E-mail-Forums for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- This e-mail and any files transmitted with it may be proprietary and are intended solely for the use of the individual or entity to whom they are addressed. If you have received this e-mail in error please notify the sender. Please note that any views or opinions presented in this e-mail are solely those of the author and do not necessarily represent those of ITT Corporation. The recipient should check this e-mail and any attachments for the presence of viruses. ITT accepts no liability for any damage caused by any virus transmitted by this e-mail. ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- 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.aspx?Pageid=E-mail-Forums for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------