Carl, Just to start things rolling: What type of things start to happen at this temperature? A lot of things; all bad! If this board is cycled on and off life will be interesting to say the least. Expect the following: discoloration debonding of traces percolation of bromides out of the laminants onto the surface delamination charring and evaporation of the epoxy resin solder joint failure (CTE) internal traces failing (CTE) and so on and so on. Yes, there are some reliability problems with exceeding the temperature rating of the board. Pay a little more for FR-4 rated at 180C, PLEASE. David A. Douthit Manager LoCan LLC Carl VanWormer wrote: > I have some FETs soldered to exposed surfaces on my board (D-squared > package). Under some conditions, they may get up around 120C (the part is > rated up to 175C). I'm not worried about the FET, but I may be playing with > fire on the board. I want to know how much fire I'm playing with . . . > The IPC maximum temperature spec for FR-4 is 120C (if I'm reading things > correctly). What type of things start to happen at this temperature? Is > this where the board starts to discolor over time, or are there physical and > electrical changes that occur in this range. Do I need to worry about long > term reliability? > > Thanks, > Carl > > Carl Van Wormer > Cipher Systems > 1815 NW 169th Place, Suite 5010 > Beaverton, OR 97006 > Phone (503)-617-7447 Fax (503)-617-6550 > > --------------------------------------------------- > 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 > ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------