Also - less features = less rule checking, risk of potential layout issues (isolations, etc), less image acquisition validations in data, plots, imaging and etch. Over all the less data features the less to verify along the fabrication path = a small cost savings in fabrication. Jeffrey Bush Sr. Principle Product Assurance Engineer Space Systems & Electronics - Performance Excellence BAE SYSTEMS INCORPORATED ELECTRONIC SOLUTIONS AND INTEGRATION 144 Daniel Webster Highway M/S MER24-116A Merrimack, NH 03054-4898 USA Tele +1 603.885.8137 Mobile +1 603.318.8056 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Pete Houwen Sent: Tuesday, April 07, 2009 9:42 AM To: [log in to unmask] Subject: Re: [TN] when do vias require a thermal relief When wave soldering, much of the metal heating is done by the solder itself. So as solder travels up the pin and hole, a large heatsink (non-relieved plane) can stop the solder flow. When reflow soldering, the board itself is heated. So even external planes and SMT pads do not need thermal relief. That's for holes/pads connected to pins/leads. Those are NOT "vias". Vias don't get a pin in them, don't need solder, there is no thermal consideration required. Best to directly connect to the plane, for electrical and fabrication concerns. For the same reason your fabricator wants to remove non-functional pads, they would rather not have themal vias. If you have a via carrying enough current to need solder fill all the way through, the thermal spokes are going to need to be large enough that they will not provide much thermal relief anyway. So the short answer is vias never need, and probably should not have, thermal relief. (but never say never) Pete --------------------------------------------------- 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 -----------------------------------------------------