John, you did not say what kind of dielectric(s) are in the capacitors. Some ceramics are unstable with thermal shocks and are sensitive to temperature changes. So if a capacitor was at -9% to begin with, and thermal stress led to -2%... You say "drifted" from nominal. Were they all at nominal before the stress? Lou Hart -----Original Message----- From: John Fahey [SMTP:[log in to unmask]] Sent: Wednesday, June 13, 2001 11:46 AM To: [log in to unmask] Subject: [TN] Capacitor Values drifting after temperature cycling Is it common to see values of capacitors drift after temperature cycling? I had a 15% ICT fallout on some caps after 48 hrs temperature (85deg) cycling. The values drifted @+/- 11% from their nominal. The component specs allow a +/- 10%, but I am curious why the moderate temperature cycling would cause a 15% failure rate for capacitor value drifting when they were tested on the ICT second time around. The ICT parameters/set up did not change and I had 100% ICT pass rate first time around. ------------------------------------------------------------------------ --------- 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 To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 1.8d 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 delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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 ---------------------------------------------------------------------------------