Tantalum capacitors are not failure proof. Ask around about tantalum failures, usually someone has a memorable story about an old tantalum capacitor that shorted.
If you buy quality electrolytics and don't store the machine in a humid shed/attic they are likely to outlast you.
Tantalum have their own issues. Yes, they live longer. But they're nice little fire starters and are much more critical than electrolytic capacitors when it comes to voltage tolerance.
It would be interesting to show the innards of an electrolytic capacitor, but as they are liquid filled... that might be a challenge. I've grown to hate Tantalum capacitors, as they will often short themselves out for no apparent reason, and take things out of service.
The past three companies I've worked for that were doing circuit board design expressly forbid the use of tantalum capacitors because they are surface mounted (SMT) two-terminal parts that have polarity. In other words, tantalum caps have a + and a - terminal and are damaged when reverse voltage is applied. Blanket ban on tantalum use was to avoid mistakes during PCB assembly in manufacturing where caps are oriented incorrectly.
Edit: Maybe I misunderstood the reason for a blanket ban of tantalums. The fact remains, the ban was real.
What are some of the places where tantalum capacitors are required and ceramic capacitors just can't get the job done?
That is some brutal power sag going on. Those waveforms would probably look a good bit different with the capacitors replaced. Thirty years is a long time for electrolitic caps, and the tantalums are probably not much better.
Part 2 re: Tantalum capacitors always being leaded parts isn't accurate, there are lots of SMT tantalum capacitors. Due to it's status as a conflict material, though, and it's unique extra-fiery failure mode when you exceed it's ratings, I tend to stick with other low-ESR chemistries like aluminum polymer electrolytic, ceramic or niobium oxide (much more stable - 95% less likely to catch fire and non-conflict, similar performance).
Tantalum capacitors are only "trivial to substitute" in some applications; as someone who works in electronic hardware, I can assure you that it is often impossible to use any other part, and achieve the same performance.
The failing electrolytic capacitor syndrome is interesting to me because I worked as a hardware designer in that period and I don't remember it being common knowledge that those components had a limited life. I do recall that we mostly used solid Tantalum capacitors with the transition to surface mount technology but I believe that was more to do with survival in the production process than long field life time.
Shorting a capacitor of sufficient size can send molten metal bits flying around as the leads melt under high current, or even make the capacitor explode. I’m all for DIY repairs, but if you’re going to do this at least wear safety goggles. Also, short the capacitor after turning the power off and before unscrewing it—that’s the time you’re most likely to complete the circuit with a fleshy part.
Edit: There might also be other bits in the system with residual power that refill the capacitor even after unplugging the mains, so a voltmeter is a good idea as well.
Interesting article, it reads like they are trying to rehabilitate the tantalum capacitor market.
Back when NetApp was got a deal to provide filers for IBM to re-label the word came from IBM that all Tantalum capacitors had to be designed out of the system. There was an interesting project in engineering to purge the designs of all tantalum capacitors. IBM's reasoning was that they had been the source of fires as I recall.
As a result I find myself always hesitating to use one (even in silly one-offs) and other engineers I've met have similar habits.
Might be a retcon. There are sometimes good reasons not to use tantalum aside from the explosion and fire inevitability.
At really high temperatures (engine computers etc) tantalum loses voltage rating down to less than 50% in some cases at the limit whereas ceramics lose capacitance with high temp (weird but true for X7R dielectric). This is a general rule of thumb and I'm sure you can find mfgrs whitepapers explaining how their expensive series is immune to this general class effect.
In the bad old days tantalum volume was like 100 times smaller for a given capacitance than a ceramic but its not the bad old days anymore and its like 3:1 ratio for some MLCC and because of voltage derating a tantalum derated to 25V (aka a 50V+ cap) might not be all that much smaller than a 25V rated MLCC. Size of cap is no longer a relevant criteria, but customers are more excited than ever about burning exploding personal electronics, so ...
Another fun one is leakage current for tantalum is about three orders of magnitude (whoa!) higher than MLCC. Its possible to build little ultra low power IoT things that sleep most of the time and a tantalum leaks more mAH than the processor but a MLCC would waste less.
High frequency response is fun because neither is inherently better but in some applications one or the other is better. Generally the MLCC is going to have a higher Q resonance at a higher frequency. If that freq is irrelevantly high to the app and EMI issues, thats a great cap, whereas maybe for some apps sometimes tantalums could be resonant, admittedly at a lower Q, in the region of freqs important to the app or EMI/EMC issues.
Not that ceramics are problem free. Piezoelectric effects are hilarious. Aging after heating drops ceramic capacitance, its possible to solder a SMD cap and watch its value drop a couple percent over the next day or so.
As with all effects you can acquire manufacturers whitepapers explaining how their extremely expensive exotic series cap can be soldered in place of another of the same family if there's a design mistake and you need to correct it in production, so sure you can pay a lot of money for tantalums that work at 230C or temperature stable ceramics.
Something I don't understand is ceramics being ceramics mean they should be good up to lava like temps and alloys being alloys mean you should be able to find something with a matching coeff of expansion thats good up to liquid metal temps, so why can't you buy ceramic caps rated to orange-hot temps? I haven't looked into it deeply enough to find out. There are practical reasons wet tantalums can't run at cutting torch temperatures but ceramics superficially don't seem to have those limits.
Higher capacity you mean (for a given volume), that and also very low leakage current so if you want to make a very efficient device then tantalum might pay off. Another reason is that electrolytic caps are usually wound aluminum sheets which act as a coil. If you don't want any parasitic inductance tantalum is better in that application (better frequency response).
A good reason not to use tantalum caps is that 10 years down the line or so they seem to transform into automatic firestarters.
But if you aren't able to correctly install parts with any polarity then the only parts that you might be able to use are resistors, coils and capacitors without polarity (which tend to be low capacity), which would make for rather boring designs.
Ceramic caps are usually very low capacity, tantalum and electrolytic caps (much) higher.
Electrolytic capacitors can dry out, boil out, oxidize, generally break down. There's many failure modes for them that can be caused by wear, age, or unuse.
A short dumps a pile of current across the capacitor. an open circuit usually just means your circuit doesn't work well.
Don't use tantalum without a careful plan to deal with this issue... why are you forced to use them instead of a modern electrolytic?
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