The best test method I have found for a multiple temp cycle test is to design a small coupon the goes on the thief of your board, we made it 10-20 holes in series and would use each drill bit a couple of times. the coupon was cut out and using a stanford 4 wire resistance measuring unit the coupon was placed in a cycle oven and the resistance measured. allowing time to stabilze between each temp rise.If the resistance increases by as little as 5 % after or during a cycle you have a crack starting. this saves cross sectioning and the fact that a cross section only looks at two very small spots aroung the hole. A far as what you can do is a big question, usualy its copper ductility or not enough copper in the hole, but as mentioned thicker boards with stange designs can be a problem. my research has shown you can all ways add more copper to the hole ( 2 to 3 oz) and it always gets you through the tests. In fact the tests I have done would convinse me if I were ever to start up a PCB shop again, the standard board would start with 1/4 oz copper and I would plate 2 oz . it gives you better fine line control , less polution from etching ( less etch) and better reliabilty. Just to confuse the issue. robert Tarzwell megadawn.com --------------------------------------------------- Technet Mail List provided as a free 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------