For those of you designing or building burn in boards, are any of you building them on Thermount material? One of our customers has shown an interest in this material for their burn in boards and we're trying to decide if that's a wise move or not. Most of their boards use 0.8mm and 0.5mm BGA's and have traditionally been built on Polyimide. The problem is that some percentage of them develop low voltage shorts in the field. Hole to internal traces may be as low as 3 mils when drill wander and material movement are at their worst but normally it's maintained at 6-mils or better. The boards are tested at 40 volts prior to shipping and all pass but some number of them will develop the field problem. CAF is suspected but I'm not so sure. The field failures develop in days or weeks rather than months. I suspect rather than CAF it may be due to the resin system itself. I understand that most Poly manufacturers use a common Poly resin from Ciba and that it has been suspected of developing this low voltage shorting issue (sulfur content I believe). Anyone out there have any comments about the situation itself or comments regarding Thermount (85RT and 55ST)? Thanks, Mark Mazzoli --------------------------------------------------- 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 -----------------------------------------------------