After years of building high powered printed circuits I found a few isuess with the mot and T/g First is if you are any where near the maximum operating temp of any material your way to hot. The Temp the lamiantors give is a max temp for a very short time. not for long periods. The material will degrade both in phisical strenght as well as voltage dialectric properties. one fr4 160 t/g I tested lowered the dialectric from 1100 volts per mil to 250 volts per mil in as little as 100 hours at the MOT. remember the T/g is the temp at which the material is going plastic, not a good thing when you are using it to carry components and sensitive copper vias and traces. I see in forums all the time designers stating with fact that FR4 can take 120-180 degrees C this is not so, take a pieace of Ffr4 AND PUT IT IN A OVEN ( NOT IN YOUR HOUSE OVEN) AND SEE WHAT IT LOOKS LIKE AFTER 30 HOURS AT MOTIt will be brown and starting to show fibers on top. Add some heat sinks or more air flow and get the temp down to a more resonable level. --------------------------------------------------- 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 -----------------------------------------------------