One of our engineers, Bill Hanna, came up with a calculator using publicly available information and from some work by Celestica that was derived from IPC. Bill gave the ok to share it, although he notes that it has not been experimentally verified. We have the same issue with design engineers wanting a lot of grounding, especially for high frequency signals, then we can't get the parts soldered and rework is difficult. I used the groupsite file cabinet to post the spreadsheet. http://ipc-technet.groupsite.com/uploads/files/x/000/046/5b7/Thermal% 20reliefs%20for%20through-holes --------------------------------------------------- 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 -----------------------------------------------------