*gasp* Useful EDN article on tantalum caps
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From: Archimedes' Lever on 5 Jun 2010 13:19 On Sat, 05 Jun 2010 09:05:19 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Z is even better. I'd like one more hour of Z but I have to service the >pellet stove today ... I could do that in my Z. :-)
From: krw on 5 Jun 2010 13:33 On Fri, 04 Jun 2010 10:59:32 -0500, Jim Yanik <jyanik(a)abuse.gov> wrote: >Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote in >news:4C091ABE.3090007(a)electrooptical.net: > >> On 6/4/2010 10:04 AM, John Larkin wrote: >>> On Fri, 04 Jun 2010 09:47:43 -0400, Phil Hobbs >>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >>> >>>> Stupid title, but actual useful info on tantalum cap behaviour: >>>> >>>> http://www.edn.com/article/509092-What_a_cap_astrophe_.php >>>> >>>> Now that there's this existence proof, maybe there'll be a bit >>>> more...perhaps someone will write them another useful article, e.g. a >>>> compendium of all two-transistor circuits. >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>> >>> Tantalums fail from excess current, namely dV/dt. MnO2 is an oxidizer >>> and tantalum is a fuel, and only a tiny ignition source sets it off. >>> They are fine for current-limited applications but firebombs if used >>> to bypass power rails. Derate them 3:1 on voltage if you must use them >>> as power bypasses. Better yet use aluminums, polymer aluminums for >>> wide-temperature appls >>> >>> John >>> >> >> The interesting thing in the article is that soldering makes large tants >> vulnerable to overvoltage failure well below their rating, and that they >> can be reconditioned (and made much more reliable) by putting a current >> limit on the power supply. That's more useful for repairs or fixing >> problems with a shipping product than for new designs, admittedly. >> Still, I thought it was kind of cool, and remarkable for being in EDN! >> >> Cheers >> >> Phil Hobbs >> > >TEKTRONIX used tantalums for many years in their scopes,and the failures >were not objectionably high. Usage was mostly on power rails,BTW. IBM used kabillions of the things for direct power rail bypassing, as well. The problems were mainly because it was almost impossible to guarantee they were stuffed the right way. They came up with all sorts of schemes, including integrated fuses in the package, to solve the problem. Last I knew, they still use tons of them (and run around in a panic when the global supply of tantalum dries up, as it does every decade or so). I still use tantalums (Aluminums, yuck!) for bulk capacitance. The only problem we're having with them is T0 shorts on 220uF 16V caps. Some circuits have a 10 or 25ohm 0603 series resistor and it takes that out.
From: krw on 5 Jun 2010 13:34 On Fri, 04 Jun 2010 13:25:20 -0700, Joerg <invalid(a)invalid.invalid> wrote: >John Larkin wrote: >> On Fri, 04 Jun 2010 09:53:36 -0700, "Paul Hovnanian P.E." >> <paul(a)hovnanian.com> wrote: >> >>> Phil Hobbs wrote: >>> >>>> On 6/4/2010 10:04 AM, John Larkin wrote: >>>>> On Fri, 04 Jun 2010 09:47:43 -0400, Phil Hobbs >>>>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >>>>> >>>>>> Stupid title, but actual useful info on tantalum cap behaviour: >>>>>> >>>>>> http://www.edn.com/article/509092-What_a_cap_astrophe_.php >>>>>> >>>>>> Now that there's this existence proof, maybe there'll be a bit >>>>>> more...perhaps someone will write them another useful article, e.g. a >>>>>> compendium of all two-transistor circuits. >>>>>> >>>>>> Cheers >>>>>> >>>>>> Phil Hobbs >>>>> Tantalums fail from excess current, namely dV/dt. MnO2 is an oxidizer >>>>> and tantalum is a fuel, and only a tiny ignition source sets it off. >>>>> They are fine for current-limited applications but firebombs if used >>>>> to bypass power rails. Derate them 3:1 on voltage if you must use them >>>>> as power bypasses. Better yet use aluminums, polymer aluminums for >>>>> wide-temperature appls >>>>> >>>>> John >>>>> >>>> The interesting thing in the article is that soldering makes large tants >>>> vulnerable to overvoltage failure well below their rating, and that they >>>> can be reconditioned (and made much more reliable) by putting a current >>>> limit on the power supply. That's more useful for repairs or fixing >>>> problems with a shipping product than for new designs, admittedly. >>>> Still, I thought it was kind of cool, and remarkable for being in EDN! >>> That might make a good argument for a properly thought out burn in >>> procedure. There's too much pressure from management to just build it and >>> ship it (airplanes included). >> >> We've had tantalums fail months or years after a product was shipped. >> On one of our VME modules, which we do burn in, well over half the >> field failures were tantalum caps. Field MTBF increased by about 3:1 >> when we fixed that problem. >> >> This is more an engineering issue than a test/burnin thing. Dry >> tantalums have to be designed in very carefully, and the manufacturers >> mostly don't want to tell you what's safe or not safe. >> > >Sounds just like LDOs :-) Phut - *BANG*! Yeah, sorta. ;-)
From: krw on 5 Jun 2010 13:37 On Sat, 05 Jun 2010 09:05:19 -0700, Joerg <invalid(a)invalid.invalid> wrote: >Michael A. Terrell wrote: >> George Herold wrote: >>> On Jun 4, 7:22 pm, John Larkin >>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> On Fri, 4 Jun 2010 16:15:49 -0700 (PDT), Glenn Gundlach >>>> >>>> >>>> >>>> >>>> >>>> <stratu...(a)yahoo.com> wrote: >>>>> On Jun 4, 2:10 pm, John Larkin >>>>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>>> On Fri, 04 Jun 2010 13:25:20 -0700, Joerg <inva...(a)invalid.invalid> >>>>>> wrote: >>>>>>> John Larkin wrote: >>>>>>>> On Fri, 04 Jun 2010 09:53:36 -0700, "Paul Hovnanian P.E." >>>>>>>> <p...(a)hovnanian.com> wrote: >>>>>>>>> Phil Hobbs wrote: >>>>>>>>>> On 6/4/2010 10:04 AM, John Larkin wrote: >>>>>>>>>>> On Fri, 04 Jun 2010 09:47:43 -0400, Phil Hobbs >>>>>>>>>>> <pcdhSpamMeSensel...(a)electrooptical.net> wrote: >>>>>>>>>>>> Stupid title, but actual useful info on tantalum cap behaviour: >>>>>>>>>>>> http://www.edn.com/article/509092-What_a_cap_astrophe_.php >>>>>>>>>>>> Now that there's this existence proof, maybe there'll be a bit >>>>>>>>>>>> more...perhaps someone will write them another useful article, e.g. a >>>>>>>>>>>> compendium of all two-transistor circuits. >>>>>>>>>>>> Cheers >>>>>>>>>>>> Phil Hobbs >>>>>>>>>>> Tantalums fail from excess current, namely dV/dt. MnO2 is an oxidizer >>>>>>>>>>> and tantalum is a fuel, and only a tiny ignition source sets it off. >>>>>>>>>>> They are fine for current-limited applications but firebombs if used >>>>>>>>>>> to bypass power rails. Derate them 3:1 on voltage if you must use them >>>>>>>>>>> as power bypasses. Better yet use aluminums, polymer aluminums for >>>>>>>>>>> wide-temperature appls >>>>>>>>>>> John >>>>>>>>>> The interesting thing in the article is that soldering makes large tants >>>>>>>>>> vulnerable to overvoltage failure well below their rating, and that they >>>>>>>>>> can be reconditioned (and made much more reliable) by putting a current >>>>>>>>>> limit on the power supply. That's more useful for repairs or fixing >>>>>>>>>> problems with a shipping product than for new designs, admittedly. >>>>>>>>>> Still, I thought it was kind of cool, and remarkable for being in EDN! >>>>>>>>> That might make a good argument for a properly thought out burn in >>>>>>>>> procedure. There's too much pressure from management to just build it and >>>>>>>>> ship it (airplanes included). >>>>>>>> We've had tantalums fail months or years after a product was shipped. >>>>> > >> On one of our VME modules, which we do burn in, well over half >>>>> the >>>>>>>> field failures were tantalum caps. Field MTBF increased by about >>>>> 3: 1 >>>>>>>> when we fixed that problem. >>>>>>>> This is more an engineering issue than a test/burnin thing. Dry >>>>>>>> tantalums have to be designed in very carefully, and the >>>>> manufacturers >>>>>>>> mostly don't want to tell you what's safe or not safe. >>>>>>> Sounds just like LDOs :-) >>>>>> Lots of LDOs need tantalum output caps to be stable. It's a >>>>>> conspiracy. >>>>>> John >>>>> How do polymer caps stack up? >>>>> G >>>> Assuming that's a serious question, and not a terrible pun, they're >>>> great, but ESR is so low that some LDOs won't like them. >>> Can't you add a bit of R? >> >> >> L is better for tantalums. >> > >Z is even better. I'd like one more hour of Z but I have to service the >pellet stove today ... Pellet stove? It'll be 90F today, and humid (T-boomers soon).
From: Joerg on 5 Jun 2010 14:22
krw(a)att.bizzzzzzzzzzzz wrote: > On Sat, 05 Jun 2010 09:05:19 -0700, Joerg <invalid(a)invalid.invalid> wrote: > >> Michael A. Terrell wrote: >>> George Herold wrote: >>>> On Jun 4, 7:22 pm, John Larkin >>>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>> On Fri, 4 Jun 2010 16:15:49 -0700 (PDT), Glenn Gundlach >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> <stratu...(a)yahoo.com> wrote: >>>>>> On Jun 4, 2:10 pm, John Larkin [...] >>>>>> How do polymer caps stack up? >>>>>> G >>>>> Assuming that's a serious question, and not a terrible pun, they're >>>>> great, but ESR is so low that some LDOs won't like them. >>>> Can't you add a bit of R? >>> >>> L is better for tantalums. >>> >> Z is even better. I'd like one more hour of Z but I have to service the >> pellet stove today ... > > Pellet stove? It'll be 90F today, and humid (T-boomers soon). We had to heat until end of May. Global warming, you know :-) Pellet stove is done, now it's the wood stove. Way easier, piece of cake. Then comes my all time favorite honey-do job, cleaning the ash vacuum <cough, cough>. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |