Ceramic X5R or X7R or similar dielectrics. Caveat - much lower esr than tant, so will affect circuit operation in applications such as linear voltage regulators or SMPS. Should always be subject to a design revue. You don't need to derate voltage by the same degree (~2.5 for tants), but the higher voltage ceramic parts will be thicker and mechanically more robust than lower voltage parts when pad geometry is optimised. From circuit design perspective, the only advantage of tants over ceramics is when you need to pack 100's or 1000's of uF in a small space. However high value tants are damn expensive. Best Regards David Greig ______________________________ GigaDyne Ltd Buchan House Carnegie Campus Dunfermline KY11 8PL United Kingdom t: +44 (0)1383 624 975 www.gigadyne.co.uk ______________________________ -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of - Bogert Sent: 13 November 2005 16:26 To: [log in to unmask] Subject: Re: [TN] Seeking Tantalum Chip Capacitor Reliability Information November 13, 2005 Thanks for all the good information. What type capacitor would you recommend as a replacement for the tantalum chip capacitor? ----- Original Message ----- From: Ingemar Hernefjord<mailto:[log in to unmask]> To: [log in to unmask]<mailto:[log in to unmask]> Sent: Sunday, November 13, 2005 11:02 AM Subject: [TN] Seeking Tantalum Chip Capacitor Reliability Information Monsigneur Bogert Here are some links to good papers about tantalum failure modes and also about reliability calculations. If you read these carefully and follow the instructions, you have 1. become a tantalum expert 2. tools for making a safer design Good luck! Ingemar Hernefjord Ericsson Microwave Systems https://www.avx.com/docs/techinfo/failure.pdf<https://www.avx.com/docs/techinfo/failure.pdf> https://www.avx.com/docs/techinfo/eqtant.pdf<https://www.avx.com/docs/techinfo/eqtant.pdf> https://www.avx.com/docs/techinfo/bsctant.pdf<https://www.avx.com/docs/techinfo/bsctant.pdf> https://www.avx.com/docs/techinfo/tantimp.pdf<https://www.avx.com/docs/techinfo/tantimp.pdf> https://www.avx.com/docs/techinfo/rmtant.pdf<https://www.avx.com/docs/techinfo/rmtant.pdf> https://www.avx.com/docs/techinfo/thrmtant.pdf<https://www.avx.com/docs/techinfo/thrmtant.pdf> -----Ursprungligt meddelande----- Från: TechNet [mailto:[log in to unmask]] För Ingemar Hernefjord Skickat: den 12 november 2005 17:47 Till: [log in to unmask]<mailto:[log in to unmask]> Ämne: [TN] SV: [TN] Seeking Tantalum Chip Capacitor Reliability Information We have had problems with exactly same cap one year ago, they broke down electrically, even exploded! I think you have a derating problem. Reported failures had to do with inrush current and heat dissipation (internal losses). We used recommended formulas for calculating correct application of series resistors, peak voltage, max reverse voltage etc. Finally, we gave up and did this: two in parallel, another two in parallel and these in series. Clumsy, yes, but we have had no problems since that. I've written a report, let's see if I can find it. Of course, various brands show different failure rates. We performed accelerated life test on two new brands. Some hundreds of each, max DC voltage at room temperature. 1 kOhm in series for each cap in order to follow leakage current and avoid direct shorts. While our standard cap began to show failures after 1 day (!!) and showed several failures to 1,000 hs, the other brand had <1 uA leakage all the way! All old caps were sent for destruction and the new brand was introduced immediately. BUT, as I said, this was a tough design with high demands on the caps, so we still got some, but very few, failures. And as the application is military, no failures are accepted the first five years in field. The above described parallel/series version has worked perfectly now for one year, not one single failure reported even after tough environmental and electrical testing. Inge -----Ursprungligt meddelande----- Från: TechNet [mailto:[log in to unmask]] För - Bogert Skickat: den 12 november 2005 14:26 Till: [log in to unmask]<mailto:[log in to unmask]> Ämne: [TN] Seeking Tantalum Chip Capacitor Reliability Information November 12, 2005 Folks, we are experiencing large number of failures of tantalum surface-mount chip capacitors (CWR06 style). The capacitors are a modified version of MIL-C55365 parts to give an extended CV range. The parts are modified 35 Volt rated parts to yield 22 microfarad, 50 volt rated parts. Reverse peak voltage for these parts is 2.5V at 85C and 5V at 25C. The failed parts were installed correctly. We checked voltage ratings, ripple current, etc. and all are OK for the application. There is a problem with board layout since the vendor hand soldered the parts to the board by applying soldering iron directly to the top surface of the capacitor rather than to the pad area (the capacitor manufacturer indicated this is not recommended). This is because the layout was flawed since the land area was not larger than the part so the pad could not be heated via the soldering iron. The vendor subsequently changed method of soldering to implement pre-heat and reflow soldering and no longer uses hand soldering. However, even with these changes, the parts are still failing. This part is a commercial version of a MIL-C-55365 part. The vendor does no burn-in electrical screening testing on the parts so we suspect our failures may be due to the normal bath-tub curve in that we are not weeding-out premature failures. Does anyone have reliability data showing what failure rates can be expected for these type capacitors for both non-electrically screened tested vice electrical screened tested parts. Also, what are the most likely failure modes for this type part and what are the failure --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask]<mailto:[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]<mailto:[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]<mailto:[log in to unmask]>: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives<http://listserv.ipc.org/archives> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/contentpage.asp?Pageid=4.3.16> for additional information, or contact Keach Sasamori at [log in to unmask]<mailto:[log in to unmask]> or 847-615-7100 ext.2815 ----------------------------------------------------- mechanisms? --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask]<mailto:[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]<mailto:[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]<mailto:[log in to unmask]>: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives<http://listserv.ipc.org/archives> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/contentpage.asp?Pageid=4.3.16> for additional information, or contact Keach Sasamori at [log in to unmask]<mailto:[log in to unmask]> or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask]<mailto:[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]<mailto:[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]<mailto:[log in to unmask]>: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives<http://listserv.ipc.org/archives> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/contentpage.asp?Pageid=4.3.16> for additional information, or contact Keach Sasamori at [log in to unmask]<mailto:[log in to unmask]> or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- -- Virus scanned by Lumison. --------------------------------------------------- Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------