The ageing effect of some dielectrics is large. It is quoted as percent per LDR. Figures can be as high as 7% per LDR. (-7% hour 1, -7% next 10 hours etc) Reset is achieved by high temperature (Curie Point?) such as soldering. So I've seen ICT fails for being too high when tested quickly after reflow. Close reading of some chip capacitor specs leads one to believe that -100% plus infinity on tolerance is a valid spec. I would look carefully at the spec of the capacitor designed in and discuss with the board designer what is needed. It is quite possible that the designer is unaware of the lack of stability in some dielectrics. Rex Rex Waygood Technical Manager PartnerTech Poole Ltd Benson Road Poole Dorset BH17 0RY United Kingdom Tel: +44 (0)1202 674333 Fax: +44 (0)1202 678028 DDI: +44 (0)1202 338222 Mob: +44 (0)7887 997403 [log in to unmask] www.PartnerTech.co.uk -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea Sent: 01 July 2008 16:18 To: [log in to unmask] Subject: Re: [TN] Ceramic Cap Value Hi Ken, We've seen this phenomenon twice in the past 4 months, high rate of ICT failure on ceramic caps and had the same issue, replacing the parts sometimes worked and sometimes didn't. We even have a painful open case on this matter. I need more clarifications from the group regarding this issue and how to get around it. The paper on aging asks to take the phenomenon into account when designing the circuitry. Does this mean the high failure rate Ken and I witnessed is borderline design? Can it be marginal testing method also? Can it be anything else that design or testing? Thanks, Ioan ------------------------------------------------------------------------------- The information contained within this e-mail and any attachments contained therein may be confidential and/or legally privileged and is for the use of the intended recipient only. If you are not the intended recipient please delete it from your system and notify the sender by return e-mail. The content of this e-mail may not be copied or disclosed to any third parties without prior permission from the sender. E-mail is susceptible to data corruption, interception, tampering and viruses. We do not accept any liability for any such incidents or any consequences thereof. --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------