So even the manufacturers think they are crap as well! - what's the point of printing 36V on a capacitor then hiding away in the datasheet that you shouldn't use it above 12V?.

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Nigel, I think that you'll never choose tantalum capacitors!?!

 

Except for the one case I suggested! - I'm even more against them now you've posted that Hitachi link!.

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As I said, I always use them after 5 V LDO regulators, that require a low ESR.
10 uF - 16 V tant caps are cheap and I find them easily. As I don't know exactly the ESR of my aluminum caps, I prefer to avoid failures!

 

Nigel Goodwin, Since your mostly opposed to Tantalums, Here is Something else you might Consider when using Electrolytics.

The Physically Bigger the cap is, Generally speaking the Lower its ESR is!

So for two caps of the Same Voltage and Capacitance, if you Need Low ESR, Use the Bigger one.

Actually, Testing my Tantalums on my "Sencore LC102", Capacitor/Inductor Analyser, this also holds true for these types. "Physically Bigger is Better in this way".
If you Have the Room.

Also, Testing a lot of NEW Electrolytics that I have just Bought, I find most of them FAIL for the ESR Test.

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I've never seen any reason to trust them?, and the lack of them now in anything I ever see seems to prove me right. Perhaps tantalums are more reliable now?, but domestic electronics manufacturers don't seem to be convinced after the previous disasters!.

I'm also somewhat dubious about using components with have a specific rating, then a warning in the datasheet not to exceed 1/3 of that rating - it seems a poor way to specify a component!.

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Actually, this problem is not as bad when they are on the outputs of IC regulators. A much worse scenario exists when they are on the "input" side. This side _usually_ connect to an even lower impedance source and the startup surge current often does these caps in. A filtering inductor in the path helps the situation greatly. IC regulators usually have current limit built into them and I often wonder if this is responsible for output tantalums surviving repeated startup surge currents.

 

I believe if you specify a quality manufacturer and use a trusted distributor you can get quality tantalums. They can be used reliably if you apply modest de-rating and watch out for repetetive surge situations. By the way, you can get fused tantalums for those who remain ultra-paranoid.

Also generally, de-rating components will improve the longevity no matter what the compopnent. So if the tantalum manufacturers are putting de-rating warnings into the dataheets, consider it a blessing. When was the last time you saw an aluminum electrolytic datasheet that read:

CAUTION: The electrolyte in this capacitor will dry out over time and cause the component to fail. It will likely be the most unreliable part in your design. Please de-rate generously to imporve longevity. Enjoy!

 

Personally, I use aluminum type at the input because they're cheaper and low ESR is required at the output to avoid oscillation.

Good observation!

 

But they don't say "while we rate this capacitor at 63V, please don't attempt to use it at more than 21V"

Admittedly electrolytics are troublesome - but less so (in my experience) than tantalums - certainly far more reliable compared to where the tantalums historically failed. Small electrolytics used as supply decouplers on PCB's hardly ever fail - tantalums did. Where electrolytics fail big time is in switchmode PSU's!.

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We are not used to look for datasheets of capacitors and resistors, as we do for ICs... but that information exists.

 

Yes, and you also need to know what charicteristics are required for your application

For example, ripple current is important when using a capacitor as a smoother on a power supply but unimportant in a timing capacitor.

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It sounds like one of tantalums advantages 'low esr' is it's biggest failing point as well? Electrolytics would self regulate their current because the ESR is higher? Am I getting the rough idea here right?

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Been telling you- their reliability is now well understood for different temps and voltages. They're used in many high end apps so their process control is quite well developed.

I'm not sure who "domestic mfgs" are nowadays since virtually everything is outsourced, but mfgs DO widely use them. They tend to be a bit more expensive and less available in throughhole pkgs. Mfgs care a LOT about cost. So big stuff (TV sets) probably won't use them. They're like gold to MP3 player, hard drive, laptop motherboard designers.

The lifespan of a tantalum cap is generally regarded longer than an aluminum electrolytic. I get the idea its window of expected lifespan and ESR rating is easier to anticipate too.

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what do you think of this?
http://indyguitarist.com/forum/index.php?topic=143.0