There does not need to be more voltage... just lots of current and a low resistance path. Bill Brooks PCB Design Engineer , C.I.D., C.I.I. Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510 -----Original Message----- From: Steve Gregory [mailto:[log in to unmask]] Sent: Tuesday, April 27, 2004 11:08 AM To: [log in to unmask] Subject: [TN] Interesting Occurance... Hi All! Just had an interesting occurance that I thought I'd share with you. We build this 14-layer assembly here that has 10 Altera FLEX 240-pin QFP's on it...4 on one side, 6 on the other. We've been building this assembly for some time now with no problems. After SMT, the board goes through AOI, gets some connectors hand soldered on, then goes to ICT. After ICT it goes into a Thermotron for some power-on thermal cycling for eight hours. Last week, after a cycle was done, the test technician went to retrieve the boards from the oven. Upon opening the oven door, he noticed this funky smell....kinda like burnt fiber glass. At one of the twelve positions in the test rack he found this: Go to http://www.stevezeva.homestead.com and look at "Smoking Hole" and "Smoking Hole 2" (NOTE: DUE TO THE GRAPHIC NATURE OF THESE IMAGES, PARENTAL DISCRETION IS ADVISED) We don't have a clue how this happened. ICT on this assembly was fine, there were no problems found in the test fixture position in the oven (other assemblies have gone through the temp cycle in the same position without a problem). And supposedly, there is only 5V and 3.3V being applied during the thermal cycle. Obviously there had to be more voltage than that to cause the kind of damage you see in the pictures, but nobody knows where it came from. Smoking Hole is a QFP on one side of the board, and Smoking Hole 2 is on the other. The leads are vaporized in the pictures. This only happened to one board, and the fixture was loaded up with another 11-assemblies. I don't expect we'll ever figure out what happened unless it somehow happens again. I know one thing, if it does, I don't want to be anywhere near the oven! Thought you might find the pictures interesting...these are $4000 images. -Steve Gregory- --------------------------------------------------- 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 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- 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 847-509-9700 ext.5315 -----------------------------------------------------