Hi Bob, As Werner mentioned, cross-sectioning to evaluate what's going on inside the PTHs is paramount. One additional point I'd like to make regarding the reliability of PTHs is drill hole quality. You don't want a rough drill hole, as this can lead to plating folds, barrel cracks, etc.... The rough drill quality is typically seen more in the smaller DHSizes, but "it depends" on the board shop.... Kind regards, Garry Morand Symmetrix Hardware Engineering EMC2 176 South Street Hopkinton, MA 01748-9103 ' 508-249-4329 * mailto:[log in to unmask] Pager: 888-377-9799 or mailto:[log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]] Sent: Monday, January 16, 2006 8:41 PM To: [log in to unmask] Subject: Re: [TN] Drill and plated hole callouts Hi Bob, The call out of finished hole size is an anachronism left over from the through-hole technology era. In modern high-density PCBs you should specify the drilled hole size (no tolerance) with a minimum plating thickness in the hole to be verified by cross-sectiong of coupons. The reliability of your vias depends on PCB thickness, drilled hole size, Cu plating thickness, Cu plating quality (verified by testing co-plated mandrel foils for tensile strength and ductiolity--not elongation). Your friend is right, electrical test is not enough. You should have coupons either IST or HATS-tested. This will be even more important with LF-soldering temperatures. You then might want to specify not only Tg, but Td and CTE(z) as well. Regards, Werner Engelmaier Engelmaier Associates, L.C. Electronic Packaging, Interconnection and Reliability Consulting 7 Jasmine Run Ormond Beach, FL 32174 USA Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904 E-mail: [log in to unmask], Website: www.engelmaier.com --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 -----------------------------------------------------