I would have to ask where the stress is coming from. Is the pad being stressed due to heat? (current through the conductor) (might be an issue since the transition point can sometimes over etch) Is the pad being stressed due to bending of the PCB? (I have seen failures due to this) Is the pad being stressed due to bending of the component lead inserted into the PTH? (I have seen failures due to this) What about a Flex PCB...the pad / conductor width ratio is important. (I have seen failures due to this) In general, if you have flexing force either on the PCB and / or component lead, then match up pad / conductor ratio as best you can. If there are no considerable flexing forces and amperage (heat dissipation) is low, then ship it! Also...when in doubt, teardrop the pads if possible. Not sure about this "rotation" dealie though Ken -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Glidden, Kevin Sent: Tuesday, October 05, 2010 3:02 PM To: [log in to unmask] Subject: [TN] PTH reliability - pad to surface trace I've been reading about PTH reliability, mainly through Paul Reid's articles and old TN posts from Werner.... If you have a PTH with a surface trace attached to the top side pad, would there be more stress (and thus propensity for cracking / separation between the pad and joining trace) at the pad / trace interface area with a smaller or larger pad size? The "pad rotation" pivots about the knee. A larger pad dia puts the pad-to-trace connection further away from the pivot point and thus the interface area would be subjected to greater deflection. Alternately, a smaller pad area (I believe 6012 requires .002" min) would have less connecting surface area ??? Or is the pad to trace interconnection not a primary failure mode when compared to barrel or corner cracks? Thanks! ______________________________________________________________________ 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.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- ______________________________________________________________________ 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.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------