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Do electrolytic capacitors have a limited shelf life? I would like to know for both aluminium and tantalum.

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4 Answers 4

up vote 17 down vote accepted

Aluminium Electrolytic Capacitors:

Epcos: 2 years, cf. this applications information

Cornell Dubilier: 3 years as per this document

Nichicon: 2 years; section 2-6 in this document

Several documents say that longer storage is well possible, but will require reforming before use. Panasonic, amongst others, has a number: Apply the rated voltage via a series resistor of 1 kOhm for 30 minutes (for example http://www.panasonic.com/industrial/components/pdf/aluminum_app_dne.pdf). There is also a military handbook about reforming stored electrolytic capacitors (formerly known as MIL-STD-1131).

Without reforming and by applying the rated voltage after a long storage duration, the reforming current might be so high that capacitors may get (too) warm and even blow up, which we do not like because we are not Beavis or Butt-Head (he he).

Tantalum Capacitors:

I couldn't find similar data after my initial search, but it seems like the usual MSL (moisture sensitivity levels) ratings for surface-mount parts are given and applicable.

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I'm surprised to see any measurable effect, but even these docs are showing minimal (<10%) changes in leakage or capacitance. I imagine if the capacitor is in a circuit with minimal allowable tolerance it may be a problem, but for most applications I'm familiar with, this wouldn't even be noticeable. –  lyndon Jan 9 '11 at 16:56
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Sure, this is just what the manufacturers tell you to make sure they don't get sued. My guess is as well that it would take much longer storage times and plenty of bad luck to have an electrolytic capacitor blow upon its first charging event after a long time. However, I know from experience that reputable manufacturers of switch-mode power supplies make sure that they don't store their capacitors too long before stuffing them into their products. When you use hundreds of thousands a year, you don't want any risk and you want your caps within spec. –  zebonaut Jan 9 '11 at 19:14

With electrolytic caps you should always pass them through LCR meter for C & ESR check (unless you are using new caps from top-end supplier).

As long as you see that C & ESR match your requirement with some margin you can use this cap no matter how old is it. This way it's safe so reuse used caps too. Just validate them all.

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Hehe, I still have some caps I desoldered in my childhood, now I have an LCR meter to see how good are they. They are from some 1970s :-) That would be funny :-D –  BarsMonster Jan 10 '11 at 0:30

Define limited: weeks, months, centuries?

For most applications the answer would be no, as long as they have been stored in conditions within spec. If the capacitors have been in hot, or very cold regions for extended time, then the electrolyte might leak out under pressure, or dry out with time. There are electronic devices that are decades old and still working just fine, capacitors and all. Sitting unused is essentially the same behavior as "shelf life."

Having said that, there is some behavior with electrolytics where the plates are "formed" when power is first applied and after sitting idle for years may need to be re-formed again. This really hasn't been an issue with capacitors for decades, so unless you're trying to use a bunch of caps that have been sitting on a shelf since 1945, I wouldn't worry about it.

I have packages of various components that are approaching 20 years old and I don't think twice before using them in new circuits.

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They definitely have a use-by date. A few years at best, eventually the electrolyte disintegrates.

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If this is true, then why do appliances I own like an old CRT monitor, still continue to work after about 15 years? Surely something like that would be packed with electrolytic capacitors. –  BG100 Jan 10 '11 at 8:21
    
I know what I've seen. I've seen banks of ageing capacitors fail one by one year after year. –  rarque Jan 10 '11 at 12:40
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Caps change over time in-circuit. Depending on how much they change (which depends on a lot of factors) and how critical their tolerance is, you may or may not see any failures in a given time frame. Give it long enough and you WILL see problems. For instance when dealing with old arcade machines, the first step with a 30 year old malfunctioning monitor is to replace all (or most) of the caps before trying anything else. That step fixes many problems and makes most other issues tractable. It's all a matter of time-frame. –  Michael Kohne Jan 10 '11 at 14:30
    
... and the type of ageing will even be differet for caps on the shelf with no voltage applied and caps in a circuit that have to take voltage changes and resulting RMS current. I can strongly recommend reading the general applications information of all the major manufacturers as the put a lot of effort in explaining what happens inside of their products. –  zebonaut Jan 10 '11 at 15:25
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The most common failure for old power supplies is dried up electrolytic filter capacitors. –  Joe May 23 '11 at 17:14

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