http://www.ieee-pses.org/symposium http://www.emc2004.org/
The derating on modern Tantalum capacitors is to run them at about 60% of the nameplate voltage. You might also look at ceramic caps if your temp range isn't too high. They keep coming down in price. Here's a link to an article on tantalum and ceramic caps http://www.elecdesign.com/Articles/ArticleID/3952/3952.html Niobium caps are a tantalum replacement. Here's a link to Vishay niobium caps http://www.vishay.com/company/press/releases/2001/010916niobium/ I haven't used a tantalum in several years. I tend to use low ESR, long life 100 deg C electrolytics when lots of C is needed and I like 100 uF ceramics for other uses. Much digression from the original question, isn't it? Dave Cuthbert Micron Technology From: [email protected] [mailto:[email protected]] On Behalf Of Rich Nute Sent: Thursday, July 15, 2004 10:53 AM To: [email protected] Cc: [email protected]; [email protected] Subject: Re: Are tantalum capacitors hazardous http://www.ieee-pses.org/symposium http://www.emc2004.org/ > Is there any safety regulation in EU that prevents usage of tantalum > capacitors in the devices that are meant for home / office environment? I > heard that tantalum capacitors are hazardous, is it so? If so in what way? Tantalum capacitors are not very tolerant to overvoltage conditions. The rule of thumb is to select the capacitor rated voltage at least twice the applied voltage. When the capacitor fails, it tends to overheat and ignite. The tantalum material and its case are not flame-retardant; indeed, they are readily ignitable and will burn until the fuel is consumed or the fire is extinguished. There are two issues. First, the flame of the burning capacitor can ignite a material located above the capacitor. We apply a keep-out volume up to 50 mm above the capacitor. If we can't apply the keep-out volume, we install a metal or Nomex flame- deflector between the cap and the material above the cap. Second, the heat of the burning cap can decompose FR4 epoxy, which then becomes conductive. If the cap is across a supply circuit, then the supply voltage will be across the conductive epoxy and a second fire may result. This fire, too, must be accounted for in the physical layout of the product. Properly applied, tantalum capacitors are reliable and effective. Best regards, Rich This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. IEEE PSES Main Website: http://www.ieee-pses.org/ To post a message send your e-mail to [email protected] Instructions for use of the list server: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. IEEE PSES Main Website: http://www.ieee-pses.org/ To post a message send your e-mail to [email protected] Instructions for use of the list server: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
