Lou, Thanks for the info. It seems consistent with what happened. The perplexing part is I found on the data sheet a statement that allows use to 125c if you derate the cap, which seems fine for the capacitance but not for the material. Go figure!! I think I have a little more digging to do on this one. Thanks again for your response........DT At 12:02 PM 10/13/00 -0400, you wrote: >Darrel, in case you are interested, regarding electrolytic capacitors, the >85 C rating means they can be baked at that temperature for 1000 hours and >the increase in equivalent series resistance (due to loss of electrolyte) >will not be more than 10%. I'm not sure what the boiling point of >electrolyte used in 85 C caps is, my recollection is that it is in the >range of 100-105 C. It has been a while since I looked, but there used to >be electrolytics rated at 105 and 125 C. >Lou Hart >---------- >From: Darrel Therriault[SMTP:[log in to unmask]] >Sent: Friday, October 13, 2000 10:58 AM >To: [log in to unmask] >Subject: Re: [TN] Baking PWA before BGA rework > >Charles, > >Good question. I just recently had some boards baked at 125c for 24 hours >to do BGA replacement >only to find when they came out of the oven that the shrink wrap on several >electrolytic caps had >cracked and peeled. I found the upper operating environment for the caps >was stated at 85c, although I >don't believe that means it is the max temp they can stand. The spec sheet >did not indicate a max >temp for prolonged periods (e.g. bake time) other then to provide an >assembly thermal profile, which had >ramp/dwell time at around 150 seconds and max temp around 260c for 30 >seconds. > >I hope I missed something in the data sheet that will shed some light on >this spec, as we rework BGAs >often and I don't want to be destroying or degrading anything on the board. > >Regards....DT > > > >At 09:34 AM 10/13/00 -0400, you wrote: > >Hello TechNetters! > > > >I am interested in the baking parameters being used for assembled PCBs > >prior to BGA rework in order to reduce risk of moisture-related damage. > > > >Component vendors often suggest 125'C for 24 hours, but this is based on > >component level requirements for drying out unmounted components. I > >have heard of baking assembled PCBs at 90'C for 48 hours. > > > >Your input is most appreciated. > >Charles. > > > >-- > >Charles Elliott, P.Eng. > >Physical Technology Engineer, Alcatel CID > >[log in to unmask] > > > >------------------------------------------------------------------------- > -------- > >TechNet Mail List provided as a free service by IPC using LISTSERV 1.8d > >To unsubscribe, send a message to [log in to unmask] with following text in > >the BODY (NOT the subject field): SIGNOFF TECHNET > >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 1.8d >To unsubscribe, send a message to [log in to unmask] with following text in >the BODY (NOT the subject field): SIGNOFF TECHNET >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 1.8d >To unsubscribe, send a message to [log in to unmask] with following text in >the BODY (NOT the subject field): SIGNOFF TECHNET >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 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF TECHNET 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 ---------------------------------------------------------------------------------