Why Electrolytics are OK - Page 1
Forum section: electronics / projects

author: katzohki
author_rank: Frequent Contributor
timestamp: August 16, 2016, 12:04:15 am
content: I'm working with some people who are gun-shy about using electrolytics (probably after the notorious events in PC power supplies). I'm looking to find some reasonable explanations as to "why it's still OK to use electrolytic capacitors." I'm not so much looking for an explanation for myself, as I am looking for links to articles or something.Thanks--K

author: katzohki
author_rank: Frequent Contributor
timestamp: August 16, 2016, 12:22:26 am
content: Quote from: blueskull on August 16, 2016, 12:10:03 amJust... like... an absolute TON of ceramics.

author: helius
author_rank: Super Contributor
timestamp: August 16, 2016, 01:20:13 am
content: Aluminum electrolytics are the only real choice for bulk supply in power supplies. For low-voltage bypass applications in computers it's certainly feasible to replace them with tantalums, but at a higher cost per CV.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 16, 2016, 05:57:42 am
content: If they really are so clueless that they cannot learn the first basics of electronic product design on their own, nor have never opened and inspected real products, trying to "assure" them sounds futile. They want to live in their own bubble and will probably hate anyone trying to burst it.IMO, this sounds similar to you trying to assure your friends that the world is not flat.The issue is of course complex and not something that is easily explained in short forum posts - or not something that can be quickly thrown as an argument, if they miss the desire and skills to actually learn the thing, which requires quite a bit of understanding about the design flow.Al elcaps, like all other components, require careful analysis before design-in. Problems are mostly due to their misuse. Just like there are tons of misuse cases with most other components, too. For some reason, people who are dumb enough not to be able to process multiple things in their heads, have picked Al elcaps as their only "case".

author: Ice-Tea
author_rank: Super Contributor
timestamp: August 16, 2016, 06:10:21 am
content: Do the math and show them.lifetime@rated temp multiplied by two for every 10° under that.Numbers don't lie.

author: Miyuki
author_rank: Frequent Contributor
timestamp: August 16, 2016, 07:24:47 am
content: Quote from: Siwastaja on August 16, 2016, 05:57:42 amIts always about money its big difference between Chinese cap with 1000 hrs rating which blows just after this time and industry grade with 10000 or even 20000 hrs rating with predictable behaviourbtw: even 450V 330uF are available as Metallized Polypropylene for applications that require service life of 100.000hrs at rated dutyNothing last forever but you can pay more and have long long life time

author: Fungus
author_rank: Super Contributor
timestamp: August 16, 2016, 11:28:29 am
content: The general rule of thumb is toneveruse them, unless you have to.Of course there's lots of situations where youhaveto, ie. When you need a lot of capacitance.Given that, the list of instructions is quite short:a) Don't buy cheap crap.b) Learn to use them properly.Part (b) mostly boils down to "watch the temperatures!" and "several smaller caps in parallel should run cooler than one big one".

author: Karel
author_rank: Super Contributor
timestamp: August 16, 2016, 11:53:33 am
content: Quote from: Fungus on August 16, 2016, 11:28:29 am+1

author: Kjelt
author_rank: Super Contributor
timestamp: August 16, 2016, 12:00:23 pm
content: Quote from: Fungus on August 16, 2016, 11:28:29 amCan you elaborate on that? Last time I searched for a 1000uF/50V replacement cap for my Keithley I saw that the cansize is one of the parameters you can directly link to the temperature lifetime parameter, eg the larger the can the larger the lifetime. So if you have one large can with a 2000 hr /105oC that would last longer than two small cans with each a 1000hr /105oC.Then I think there will also be something like the weakest link theory, the more elco's you use the chance becomes higher the product will fail earlier since the weakest elco will be the first to go.

author: Fungus
author_rank: Super Contributor
timestamp: August 16, 2016, 12:37:07 pm
content: Quote from: Kjelt on August 16, 2016, 12:00:23 pmIt's all down to ESR: Multiple caps in parallel can have a lower overall ESR than one big one. It's the ESR that heats them up and shortens their life.There are big caps with very low ESR,yes, but how much do they cost? It's all down to a cost/design/space analysis.

author: dannyf
author_rank: Super Contributor
timestamp: August 16, 2016, 12:37:48 pm
content: Just as walking and horse riding are perfectly OK in an era of jets and super cars: different needs for different applications.

author: Fungus
author_rank: Super Contributor
timestamp: August 16, 2016, 12:58:52 pm
content: Quote from: Fungus on August 16, 2016, 12:37:07 pmDave did a whole video on this:

author: Kjelt
author_rank: Super Contributor
timestamp: August 16, 2016, 01:33:08 pm
content: thanks, saw that video a while back forgot about it.

author: rsjsouza
author_rank: Super Contributor
timestamp: August 16, 2016, 01:42:06 pm
content: Searching for "aluminum electrolytic capacitors lifetime" one can find some useful references on the web:http://www.illinoiscapacitor.com/pdf/Papers/Life%20expectancy%20of%20Aluminum%20electrolytic%20capacitors.pdfhttp://www.mouser.com/pdfdocs/ELNAReliabilityAlumElecCaps.pdfhttp://www.cde.com/resources/catalogs/AEappGUIDE.pdf(and more)A calculator:http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx

author: Fungus
author_rank: Super Contributor
timestamp: August 16, 2016, 01:46:36 pm
content: One question I haven't seen answered is about the shelf life of electrolytics.Do they still dry out if I don't use the device much?

author: madires
author_rank: Super Contributor
timestamp: August 16, 2016, 02:20:54 pm
content: Some datasheets state a shelf life of a year or two before a reforming should be done. But who does reforming electrolytic caps? I've got a lot of old electrolytics in my "warehouse" (20+ years), but only a few went bad, none leaked. The main issue is the degrading of the oxide layer, when the cap isn't in use. And the second issue on the list is the stability of the electrolyte. Remember the PC mainboards with tons of bad and bulged caps several years ago (capacitor plague)? If someone asks for preventive maintenance of unused devices stored in the cabinet, I'd suggest to run a device about half an hour every 3 or 6 months. What do you think about that?

author: rsjsouza
author_rank: Super Contributor
timestamp: August 16, 2016, 02:24:19 pm
content: Quote from: Fungus on August 16, 2016, 01:46:36 pmFungus, this is still the case. Despite the technology advanced a lot over the years, nothing is absolutely sealed "for life" - not even electrolytics. I don't have data, but seeing typical issues on repair I believe the physical interfaces between the casing, terminals and the seal are the largest contributors to reduce the lifespan of capacitors with non-solid dielectrics (electrolytic/tantalum), especially on a soldered part which went through a thermal stress during soldering. Despite that, the choice of materials and the precision of machinery evolved over the years and definitely improved the lifespan by a large margin. A minor contributor is the casing itself, where material can seep through or be adsorbed (especially in lower quality brands).Obviously all that considering the device or parts are not stored on a boiler or deep freezer, which may facilitate chemical interactions inside the device and bring physical tolerances outside of their rated specifications due to thermal expansion/compression.There may be other factors I forgot.

author: Fungus
author_rank: Super Contributor
timestamp: August 16, 2016, 03:00:43 pm
content: Quote from: madires on August 16, 2016, 02:20:54 pmInteresting...Damned if you use them, damned if you don't.

author: katzohki
author_rank: Frequent Contributor
timestamp: August 16, 2016, 03:23:10 pm
content: Thanks guys, I think I've got what I need. Looks like the derating at reduced temperature is going to be the strong argument.Very much a "Peter Principle" situation that I'm in. There's a lot of superstition at this company, looks like this is going to be my first crusade.

author: Cyberdragon
author_rank: Super Contributor
timestamp: August 16, 2016, 05:52:45 pm
content: Dude, alot of my stuff still has 40 to 60 year old electrolytics and they still work fine (usualy metal can ones). Strangly, some cardboard ones are still working (most fail, but some still work, possibly because they have a metal can underneath). A lot of these are paired with tubes and exposed to heat yet it doesn't seem to harm them.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 16, 2016, 07:00:42 pm
content: If you can keep them cool they can last for decades. Heat is the number one issue by far. From memory it's something like lifetime halving for every 10 degrees over 40C

author: Ice-Tea
author_rank: Super Contributor
timestamp: August 16, 2016, 07:28:22 pm
content: Quote from: mikeselectricstuff on August 16, 2016, 07:00:42 pmAFAIK, it's the other way around: a 10kh cap rated at 105C will last 20kh@95, 40k@85 etc etc.Again AFAIK, this is a worst case: there are additional modifiers for lower-than-rated voltage and ripple current. But the main contributing factor remains temp. So, as a fast approximation-annex-worst-case, halving for every 10C works fine.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 17, 2016, 05:19:55 am
content: Quote from: katzohki on August 16, 2016, 03:23:10 pmDo you really need this crusade? It appears that they have never actually designed anything. Talk is cheap. Let it be that way, and just let them continue talking in the coffee room while you could continue actually doing things?The general rule of "never" using elcaps if not absolutely necessary is actually a good one - for any component! Electronic design takes a lot of time, and there are very few components that actually can be "just added in place" without thinking about it.Actually, aluminum electrolytic caps are rather easy in this regard - there are many places and situations they can be just thrown in without many problems arising with some experience. This is not something that could be recommended, but with many other capacitor types, it's much worse.When people talk about aluminium elcaps dying on the motherboards, they sometimes even compare them with tantalums, which is ridiculous - if they knew what they are talking about, they would know that replacing those elcaps with tantalums would cause them to blow up spectacularly in flames within hours!Let me give you an example how designing in an aluminum elcap is sometimes the easiest. Designing without actually understanding is not recommended, but it does happen, and we all do it to some extent, by following some "rules of thumb".In the case of a DC input bulk bypassing, using an elcapisa rule of thumb, and for real reasons!If you were to add a bulk input cap for a power supply wire inductance bypassing in a product with a DC input without doing much analysis and without too much prior knowledge, aluminium elcap has the highest chance to go right.- If you threw in a tantalum, it would blow up in flames randomly after some time (x number of power-ons), because you didn't analyze the peak current during power-on (a hugely critical parameter on tantalums), or you didn't know that you need to derate the voltageandtemperature by unbelievably huge margins, because the manufacturers have agreed on an insane way to specify their products, not applicable to any other component type (massive MTBF with rated specs).- If you threw in an MLCC, it would blow up as a short circuit or low-value resistor, possibly glowing like a light bulb and igniting nearby materials, because you didn't know that you shouldn't pick large case sizes (after all, they are on the market), you didn't analyze the PCB flexing near the edges (where input bypass caps usually are) due to mounting screws, and you didn't know about the right soldering profile (maybe you hand soldered a few prototypes)- Also, if you threw in a MLCC, the chances would be you get too much parasitic ringing with cable inductances, blowing up some semiconductors- Standard, good old elcap requires the least amount of analysis. The ESR is almost guaranteed high enough so it dampens the LC circuit. It does not die on slight overvoltage spikes, and does not require massive voltage derating. It easily provides enough capacitance in small enough size and cost so that when you just throw in something, you probably have enough, without doing careful analysis of how much is exactly needed. If does not heat up in this application; and if you follow and derate the temperature specoften even printed on the freaking product itself, a feat commonly know to even most total hobbyists with no experience whatsoever, the chances are you get a product that will outlive the application.Designing electronics is a strange mixture of understanding and analyzing everything, and just "following some rules". When just following the rules, it's paramount that you follow the correct rules; it helps if you have seen and done enough designs to justify that. For example, tearing down used equipment, especially failed, gives good understanding how things are designedin the real world, what works and what does not.I have seen people who talk big like "78xx regulators are not used by the industry", or, like this thread shows, "elcaps should not be used". These people have so little real experience that they should be learning themselves, not giving false advice to others.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 17, 2016, 06:40:52 am
content: I'd certainly agree that elects should be avoided where there is a reasonable alternative, but each case needs to be looked at based on all criteria - electrical, physical, cost etc.For anything below about 10uf at 25V, ceramics are usually a good alternative at similar cost so nowadays teher is rarely a reason to use small electrolytics, except maybe in all through-hole designs.Above that, aluminium or tantalum polymer generally offer superior performance, but at significantly higher cost. their lower ESR may mean you can use a lower value.You can also make other design decisions to reduce reliance on them - e.g. using a higher frequency switching regulator allows lower value ceramics to be used instead of electrolytics. There are plenty of cheap switching regs designed for ceramic caps these days, so little reason to use dinousaurs like MC34063 or the older NS Simple Switcher series, at least at lower powers.

author: katzohki
author_rank: Frequent Contributor
timestamp: August 17, 2016, 04:20:17 pm
content: Quote from: Siwastaja on August 17, 2016, 05:19:55 amSort of a joke about making it a "crusade" really. If it weren't my supervisors doing a review of my board I would just continue on. Funny that you should mention DC input bulk bypassing, as that is exactly what I was using it for. And funny that you should mention tantalums, as they were brought up as an alternative!It seems like the standard practice is to use huge MLCCs, which I'm not a big fan of either. I've had success with MLCCs in the application when designing miniature power supplies, but it's not my preference by any means.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 17, 2016, 05:40:39 pm
content: Show them this thread, just for laughs. It should hurt a little bit to see that strangers on the internet expert forum call them incompetent idiots.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 17, 2016, 05:55:33 pm
content: If you have to work with tantalums, using a series resistor to limit the inrush current works as long as the voltage drop and power loss in the resistor is not too much. Locating the resistor in series with the capacitor only may make the load ripple bypassing too ineffective (because the current needs to be limited quite a lot!), so you'd need to place the resistor in series with the power input instead, causing resistive losses all the time. Although, this would be a nice RC filter for noise, and also a good dampener for any LC effects. If you need to add a TVS (which would be a very good idea with tantalums), this same resistor would double as the current-limiting element for the protection; also helping with any LC ringing when the TVS protects.With just a random* elcap thrown in, you would probably have a simple, small, robust low-cost solution, totally industry proven in almost all tech fields, that would last for at least two decades most likely.*) Well not quite, but with much less design analysis than a tantalum solution30, even 50 year old products utilizing electrolytics as bulk DC input caps are mostly just fine. Those utilizing tantalums have poor track record. It's said that tantalums these days are much better, and when correctly designed in, there shouldn't be any issue, but the evidence is not yet there and not completely conclusive. So why bother? For me, tantalum is one of those things that's only designed in when absolutely necessary. (There are multiple threads about tantalums on the forum, you can easily find them. There are also ethical reasons not to use them.)MLCCs may also require series resistors (in series with the caps in this case, not the supply necessarily), not because they wouldn't be ok with the inrush current, but because LC ringing can actually happen because the ESR is so small.Often a parallel combination of an elcap (for its high esr for dampening!) and a very small MLCC (high-frequency bypassing) is used in the real world.I'm sorry that your boss is incompetent and cannot admit it. This happens way too often.

author: David Hess
author_rank: Super Contributor
timestamp: August 18, 2016, 05:26:13 am
content: When properly derated, aluminum electrolytic capacitors last decades. I think what has changed is that modern designs have higher power densities and aluminum electrolytic capacitors have gotten better specified so it is now possible to use them at high ripple currents for a guaranteed but limited number of hours and manufacturer's take advantage of this. If you want to build a 10 or 20 year design using aluminum electrolytic capacitors, then you still can.Tantalum capacitors need to be derated as well. They have voltage, ripple current, and surge current limits which need to be observed. Plastic encapsulated tantalum capacitors also suffer from thermal cycling.Now someone explain to me what limits the operating life of polymer aluminum and tantalum electrolytic capacitors.

author: Zero999
author_rank: Super Contributor
timestamp: August 18, 2016, 08:54:11 am
content: People always talk about tantalum capacitors blowing up and emitting smoke but I've never experienced this myself. I've seen far more electrolytic capacitors pop than tantalums.I still don't see point of avoiding electrolytic capacitors. They are cost effective and very reliable when properly used.

author: setq
author_rank: Frequent Contributor
timestamp: August 18, 2016, 09:42:40 am
content: If it's a datapoint, I have actually tried desperately to make some of the AVX TAJ tants explode. I can't do it. They get hot and that's it. No sign of combustion. Reverse over-voltage: nothing. Forward over-voltage: nothing. 2A of current going through one (obviously it has broken down by then), it just gets hot and desolders itself and falls off the breadboard. They don't even darken!And there went my demonstration of the dangers of tantalum capacitors...Now electrolytics: I've nearly lost an eye a couple of times with those bastards. Plus an old Sprague one actually blew the case off a Tek 453 I was working on. However the former was human error during prototyping and the latter was 45 years old.Ergo, go on ESR, rippple current, size and budget if you ask me.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 18, 2016, 12:39:21 pm
content: Quote from: Hero999 on August 18, 2016, 08:54:11 amProbably a bias coming up from the fact that aluminum electrolytics are used about 10000x more frequently, and more in demanding places (ripple & inrush current & voltage peaks) where tantalum wouldn't work at all. This is because almost all professional designers know to be careful with tantalums, they don't usually even try to use them in "iffy" places, so there is nothing to blow up. They get designed in mostly when a datasheet exactly says that "put this tantalum cap here" (after a current-limited LDO supply, for example). This all happens because, as you have noticed, people have heard about the tantalum issues.Al elcaps, instead, are very widely used in demanding places with little or no derating whatsoever, or even overrated - or using non-brand, knowingly bad parts for cost savings. If tantalums were used in the same way (so that your comparison would be unbiased), you'd see nothing working at all due to the tantalums.Last time I tried to blow up an AVX tantalum using serious overvoltage, it didn't go up in flames, but emitted beautiful pink smoke.But the MTBF data is there. It's hard to reach 100% failure rate (to demonstrate how easily they blow up; they don't blow upthateasily), but if you don't know exactly what you are doing and have thousands of units out in the wild, you'll still face problems.

author: Pjotr
author_rank: Frequent Contributor
timestamp: August 18, 2016, 12:41:26 pm
content: Those were the days. The old "tear drop" tants could give quite a spectacular performanceIMO tants will disappear soon for use in new stuff with the further evolution of hybrid polymer alu elcaps.Lang time ago you learned the inns and outs of standard alu electrolytic caps and how to use them. Same as you did with every other electronic part. Seems that with a myriad of modern "better" alternative capacitors that species is forgotten.

author: madires
author_rank: Super Contributor
timestamp: August 18, 2016, 01:24:16 pm
content: I think I must be lucky, since I haven't had any issues with tantalum caps the last 20+ years. The old TTL stuff I've built back then had plenty of tantalums for bypassing. Mostly I've used 16V types for the 5V TTL ICs.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 18, 2016, 05:59:18 pm
content: Quote from: madires on August 18, 2016, 01:24:16 pmMaybe not because of luck, but because, you know,design? Those tants are behind a linear regulator circuit which offers proper current limiting, and derated properly. The designer has most likely understood what they were doing. (It may be a bit of luck, in addition; tantalums might have failed in one per 1000 units, for example.)The point is not that tantalums are bad. They are just used in far, far fewer places, because they are more limited by what they can handle, and require more derating and general understanding when designing. In addition they are expensive and ethically problematic, which limits their use even more. They also can't handle high temperatures, the #1 reason why aluminium elcaps most often fail - so practically in 99% of the cases where al elcap failed, tantalum wouldn't have been a suitable alternative.Person who blindly asserts as a blanket statement that aluminium electrolytic caps are not OK in the DC input bulk supply, is most likely completely unable to design in a tantalum cap for the same purpose.Counting how many components of each type have gone bad is super biased and utterly non-informative. Components constructed from my feces must be very robust because I have never seen one blow up!

author: Kjelt
author_rank: Super Contributor
timestamp: August 18, 2016, 07:09:16 pm
content: Most time I do see tantalums in equipment they are in rather expensive gear with enormous lifetime expectancy.So why would that be then I wonder ?

author: Kjelt
author_rank: Super Contributor
timestamp: August 18, 2016, 07:20:48 pm
content: Some more tantalum facts (also used heavily in military and aero/space applications, why would that be I wonder if they are so bad)Wow1: there are tantalums that can operate in 200oC. Never seen electrolytes with higher then 125oC spec.Wow2: a tantalum has a self healing effect.http://www.vishay.com/docs/40110/faq.pdfQuote

author: setq
author_rank: Frequent Contributor
timestamp: August 18, 2016, 08:02:48 pm
content: Have you seen the price of some of them? Fancy paying £60 for a capacitor? Noooo

author: chris_leyson
author_rank: Super Contributor
timestamp: August 18, 2016, 08:43:15 pm
content: Tantalum is a conflict mineral and the guys I work for have been told not to supply products containing Tantalum caps by a very large european company.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 18, 2016, 08:58:28 pm
content: Tantalum polymer caps don't have any of the incendiary problems of the older ones.Interesting talk on the subject ( and other caps)https://youtu.be/ZAbOHFYRFGg?t=1345

author: helius
author_rank: Super Contributor
timestamp: August 18, 2016, 10:15:38 pm
content: Quote from: chris_leyson on August 18, 2016, 08:43:15 pmTin is a conflict mineral. Do you still use solder?(The conflict minerals which are being extracted by warlords in the Eastern Congo are tungsten, tin, tantalum, and gold. 3T + gold)

author: katzohki
author_rank: Frequent Contributor
timestamp: August 18, 2016, 11:46:00 pm
content: Surprised no one brought up the whole DC Offset effect of MLCCs as a reason to not use those...

author: chris_leyson
author_rank: Super Contributor
timestamp: August 18, 2016, 11:49:17 pm
content: Thanks heliusYep I still use tin but in smaller amounts these days, SMT mostlyTo get back onto topic, there is nothing wrong using electrolytics as long as you take ambient temperature, ripple current, ESR, self heating and lifetime into account and then there is size and cost, it all depends on the application. Katzohki there is no simple answer to your question it's far too vauge, maybe if you told us in what application or for what reason your colleages refuse to use electrolytics that would help. You should see the mess that failed MLCCs make, small fire turns that bit of your PCB into burnt toast with soot everywhere, and they think electrolytics are bad !!

author: katzohki
author_rank: Frequent Contributor
timestamp: August 19, 2016, 12:09:44 am
content: Chris-My guess is that it's a superstition stemming from the company culture of 1) only entering the electronics industry recently and 2) habit of exclusively hiring recent grads (not that I have anything against that, just when your company has limited electronics expertise...).I mentioned elsewhere, but the application is DC blocking in front of a RF tuned microstrip... haha just kidding it's bulk capacitance for LDO.

author: helius
author_rank: Super Contributor
timestamp: August 19, 2016, 12:18:03 am
content: Quote from: mikeselectricstuff on August 18, 2016, 08:58:28 pmVery interesting video. At the very end of the tantalum section he says that (with manganese dioxide cathodes) inrush current is actually not the cause of failure: failure is caused by voltage spikes higher than the forming voltage of the dielectric. So once a tantalum is installed and soldered in, all failures should occur during burn-in test. Once the assembly is fully burned in, additional capacitor failures are not caused through aging, only by changes in the circuit that allow higher voltage spikes than the capacitor has experienced since it was soldered.This is interesting because I have seen chip tantalums that exploded in used equipment that was certainly burned-in at the factory. If what he says is correct, then two conclusions seem evident: the first is that the burned capacitors are the symptom and not the cause. Other changes have happened in the circuit that triggered the tantalums to ignite. The second possibility is that thermal or mechanical stress great enough to fracture the dielectric has happened during the equipment's life. After this happens, the capacitor can ignite even without a voltage spike.

author: bson
author_rank: Unknown
timestamp: August 19, 2016, 02:27:51 am
content: Quote from: Siwastaja on August 18, 2016, 05:59:18 pmThey steal office supplies or something?

author: David Hess
author_rank: Super Contributor
timestamp: August 19, 2016, 06:04:21 am
content: Quote from: madires on August 18, 2016, 01:24:16 pmIncreased voltage derating increases the capability of the solid tantalum capacitor self healing mechanism to work without thermally running away. Almost all of the failures I have seen involved 6.3 volt capacitors used at 5 volts and 16 volt capacitors used at 15 volts.In tests AVX did, significant voltage derating effectively reduced the surge current failure rate to zero.Quote from: Kjelt on August 18, 2016, 07:20:48 pmNaturally Vishay would say that. They are as bad as Texas Instruments.NASA found that solid tantalum capacitors rated above 20 volts suffer from age related field crystallization leading to an increase in defect size. AVX documented failures in dipped epoxy parts do to stress related fractures which may explain the mysterious failure of solid tantalum capacitors which is not surge related.These problems can be handled by the self healing capability of the capacitors however lack of voltage derating leads to an increase in destructive thermal runaway.Quote from: helius on August 19, 2016, 12:18:03 amThat is a great video.What he says is that voltage breakdown occurs across defects in the dielectric and excessive heating from high current prevents successful self healing. New stress related defects are created by temperature cycling during soldering.The whole thing about not needing to derate polymer tantalum capacitors is what they said about solid tantalums when they were introduced.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 19, 2016, 07:09:26 am
content: Quote from: Kjelt on August 18, 2016, 07:09:16 pmBecause of the price of both the tantalums themselves, and the knowhow to buy the right parts and design them in the right places with correct calculations.Tantalums indeed are high-end stuff.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 19, 2016, 07:12:31 am
content: Quote from: katzohki on August 18, 2016, 11:46:00 pmA good point. Not a point for not using them, but a very valid point about how the design is not straightforward, and again, requires more knowledge and analysis.This effect brings the price and physical size up, as you need larger caps than originally calculated. You also need to be knowledgeable enough to avoid the worst types (like Y5V) altogether, even from good manufacturers.The point is, I always cringe when people go "electrolytic caps are only fine if you really know what you are doing". This is true withallcaps, and in many cases, aluminum elcaps are the ones withleasthassle and risks, if you understand the big picture, as you really should when designing electronics.

author: Fungus
author_rank: Super Contributor
timestamp: August 19, 2016, 08:08:24 am
content: Quote from: Siwastaja on August 19, 2016, 07:12:31 amWhat about leakage? Nobody's mentioned that yet.Elecrolytics usually have large leakage.

author: Ammar
author_rank: Regular Contributor
timestamp: August 19, 2016, 08:19:57 am
content: They are the worst. You just don't have much other choice when you need 470uF.

author: Pjotr
author_rank: Frequent Contributor
timestamp: August 19, 2016, 08:33:52 am
content: Quote from: Fungus on August 19, 2016, 08:08:24 amReally? Do they?Did just a verification test a few weeks ago: A brand new 2200uF/25V standard 105 degC Panasonic wet alu cap right out of the box (in this case a bag) was formed at 20V for 8 hours. After this 8 hours charging current (= leakage current) was measured < 10 nA. Then the cap was left alone to look at discharge behaviour due to leakage. After 6 hours, open voltage did droop to 18.6V and after a week! to 16V. After much longer forming, say days, these figures become still a lot better. To my experience all standard alu caps from the last 20 years from renowned manufacturers do show this behaviour as normal.Most leakage is often not internal to the cap but external: Pollution, board leakage etc.

author: tautech
author_rank: Super Contributor
timestamp: August 19, 2016, 09:30:03 am
content: Quote from: Fungus on August 19, 2016, 08:08:24 amI dare you to handle a 200V rated 2200uF cap charged to 150V the night before.Or check if a SMPS primary side cap is holding any charge with your finger.Or course we don't put bleeder resistors across caps like these for no good reason. They're dangerous. Period.

author: Fungus
author_rank: Super Contributor
timestamp: August 19, 2016, 09:41:49 am
content: Quote from: tautech on August 19, 2016, 09:30:03 amOK, maybe I should have said "high leakagecompared to other types".

author: Siwastaja
author_rank: Super Contributor
timestamp: August 19, 2016, 05:10:50 pm
content: This should be linked here because it's highly relevant:https://www.eevblog.com/forum/projects/help-me-get-rid-of-these-transients!/

author: Messtechniker
author_rank: Frequent Contributor
timestamp: August 19, 2016, 05:19:15 pm
content: Before continuing this discussion we esteemed members should absorb some of this:https://en.wikipedia.org/wiki/Capacitor_plague#End_of_the_plagueAnd in particular Section 4.2. This explains why non-solid electrolytics havegained such a bad reputation and why we will continue to suffer for a very long time.Yours - Messtechniker

author: zapta
author_rank: Super Contributor
timestamp: August 19, 2016, 05:38:27 pm
content: Apropos Electrolytic, Mr Carlson shows here how to remove them without desoldering. I this example he also replaces them with tantalum.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 19, 2016, 05:52:19 pm
content: Quote from: zapta on August 19, 2016, 05:38:27 pmIncompetence easily leads to the level of stupidness that makes you randomly replace 35V rated elcaps with 20V tants on the 15V line, reciting that this is "absolutely fine", although justeven reading the freaking datasheet- or at least the application note - would have probably told him that the recommended operating voltage for a 20V tant is around 10V.Of course, when the equipment is for the show in the lab and mainly unused, the reduced lifetime of this "fix" won't likely be a problem.

author: tautech
author_rank: Super Contributor
timestamp: August 19, 2016, 09:06:39 pm
content: Quote from: Fungus on August 19, 2016, 09:41:49 amPlease modify your post.You have quoted me with something I DID NOT SAY.

author: zapta
author_rank: Super Contributor
timestamp: August 20, 2016, 02:17:27 am
content: Quote from: Siwastaja on August 19, 2016, 05:52:19 pmHmm, incompetence, stupidness, random, ...I would bet that Mr Calson can teach you a trick or two.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 20, 2016, 06:50:56 am
content: Quote from: zapta on August 20, 2016, 02:17:27 amI don't know him. Never watched his videos. Never even heard of him. Don't know why I should. This video was about teaching a trick which was complete bullshit, completely lacking the basic design skills to do such a modification; so I'm not sure why I would want to learn any more "tricks".Where is the analysis of ripple and inrush current, hugely important in such a modification? Where is the analysis of working voltage and voltage transients,extremelyimportant with tantalum caps? Oh yeah, it was there: "absolutely fine"; although, this "deep" analysis is absolutely wrong, and you'd know it if you even managed to read the datasheet.Not knowing the exact part he was using, you can still google "tantalum datasheet" to find an example:http://www.vishay.com/docs/40002/293d.pdf. On page 10, it says that the 20V cap is fine up to 12V, or 10V in more demanding conditions. Randomly replacing, you can't be sure about the conditions, and 15V is really pushing it with any 20V tantalum. You'd really know this if you hadanyexperience with designing with tantalums. Basic knowledge!The mechanical part of the video is bullshit too. May work with some random cap with suitable legs. Makes a nice demo, but clearly not a real-world thing. As some commenters say, it does not work for them but lifts traces - I'm not surprised hearing that! Violently pulling out soldered components without melting the solder and explaining thatmelting the solder would risk lifting the tracesis worth a double facepalm.Maybe he's very competent otherwise, I don't know and I'm not too interested. However, at quick glance, it appears this is more about the cult of personality, instead of a really informative video. Because this is total and utter shit from the beginning to the end, sorry - although it looks nice and professional, and gives you that warm feeling of professinalism...But there are many informative and correct electronic engineering videos, also in high production quality, such as EEVblog.Sorry about joining the discussion of this near-off-topic video.

author: technotronix
author_rank: Regular Contributor
timestamp: August 20, 2016, 07:30:45 am
content: I found this page related to your query. May this will help.http://www.nmr.mgh.harvard.edu/~reese/electrolytics/